Muktol

If you want to use a cmc2 spell to give double strike to a creature I would recommend "Temur Battle Rage", otherwise I would use "Assault Strobe". It's a sorcery instead of an instant but costs one mana less to play.
"Dragon Mantle" might be traded for "Madcap Skills". You loose the ability to buff your enchanted creature with spare mana (spare mana really doesn't happen all too often in my opinion) but the enchanted creature will be much harder to block for your opponent.
"Skullcrack" can be put into the sideboard for use against lifegain decks. Use a simple "Lightning Bolt" or, if you want a cmc2 spell that can damage both player and creature, "Searing Blaze".

Greetings
Muktol

2 ways to make this deck more effective. Either you add some more aggressive cards and try to lower the mana-curve or you add more control/ removal spells.
Personally I'm building more aggressive decks at the moment, a R/G prowess/ heroic built can be seen here: http://www.mtgvault.com/muktol/decks/rg-heroic-prowess/

Greetings
Muktol

I can only give you some suggestions based on my own Krenko commander deck (http://www.mtgvault.com/muktol/decks/edh-krenko-mob-boss/).
Creatures: Battle Squadron; Goblin Piledriver; Moggcatcher; Purphoros, God of the Forge; Warren Instigator
Instant/ Sorcerys: Ruination, Vandalblast, Chaos Warp, Dangerous Wager, Massive Raid
Artifacts: Konda's Banner, Magewright's Stone, Thornbite Staff, Thousand-Year Elixir
Enchantments: Blood Moon, Boggart Shenanigans, Shared Animosity

Greetings
Muktol

Taking out "Pyreheart Wolf" will costs your opponent at last 2 spells (or one exile spell but most of those are expensive to play) as he has undying.
I would use some removal spells instead of "Fog". Fog buys you one turn but that normally doesn't solve a problem. A removal can take it out or, like "Lightning Bolt" deal the last damage to ensure your victory.

As you are playing with many cheap and fast goblins and a lot of summoning spells like "Dragon Fodder" I would switch "Hammerhand" for "Dynacharge", "Weapon Surge" or something similar. I also would try to up the number of "Goblin Bushwhacker" by 1-2 as he's simply one of the best goblins available.
14 lands seem to few, I would try to get add 2-4 additional's, otherwise it might be hard to e.g. cast "Dragon Fodder" and a kicked "Goblin Bushwhacker" to give those tokens +1/+0 and haste.

Some further suggestions:
Mogg War Marshal, Caterwauling Boggart, Skirk Prospector, Foundry Street Denizen, Mardu Scout, Mudbutton Clanger
Dangerous Wager, Massive Raid

Greetings
Muktol

A short deck description and how to play would give us hints about the budget, legality and so on.

The problem with "Huntmaster of the Fells" is that he doesn't get along to good with "Immerwolf", also he's quite expensive ($).

I totally agree with WD40 about the number of lands. Depending on your mana-curve you should try to add 4-6 lands. "Doubling Chant" can be removed and 1-2 "Overrun" can be dropped (You don't want those on your starting hand). As for your manabase, I would try to add some additional duallands (preferably those that don't enter tapped), "Rootbound Crag" would be one of the cheaper ($) duals available.
I would not switch "Full Moon's Rise" for Rancor, at last not all of them. A Single trampling creature is fine but a horde of angry werewolf that all have trample and can be regenerated by sacrificing this enchantment is real scary.

I would either remove "Gatstaf Shepherd" or switch to 2-3 "Pyreheart Wolf". He is no werewolf but forces your opponent to block one of your creatures with two of his and the chances are high that he won't be able to do so.

Lower the number of "Instigator Gang" by one, it's a finisher and you won't need it on your starting hand.

Some further suggestions:
Lightning Bolt, Searing Blaze, Vines of Vastwood, Ranger's Guile

Greetings
Muktol

If you need some carddraw you could try "Harmonize" or "Hunter's Insight".

If help is needed the you should add a proper deck description where you describe your problems, strategy, budget, and so on ;)

Greetings
Mutkol

I would sideboard "Daybreak Ranger" because the normal removal against fliers is to situated and when he get's transformed you normally don't need him any more. A buffed "Kruin Outlaw" will normally swing for more then enough damage so that you won't have to remove a single creature. Also remove "Gatstaf Shepherd" and "Lambholt Elder".

Replacement for the free slots could be:
Ghor-Clan Rampager ... Not as creature but as buff. It's no spell but an activated ability.
Young Wolf ...personally I like Young Wolf more than Wolfbitten Captive. You don't have to pay to make him big, he has undying and benefits from transformed Mayor of Avabruck and Immerwolf, though not of the untransformed Mayor
Lightning Bolt/ Searing Blaze ... some removal that can also do damage to a player is always a good idea
Vines of Vastwood/ Ranger's Guile ... protection against your opponents removal spells.

If you need some cheap ($) duallands that don't enter tapped "Rootbound Crag" or "Gruul Turf" (if you play it after you have already tapped a land for mana and and take back the tapped land) might be interesting for you.

Greetings
Muktol

Just for information (I'm pretty sure you know this but not everybody else that might look at this deck):
The copies of created with "Grapeshot" won't activate "Monastery Mentor" or "Young Pyromancer" ability's, because those 2 require spells to be cast, and copies are just played, not cast.

Also your 'deck description' is slightly outdated as you list "Desperate Ritual" as a spell but don't have it in your deck.

Greetings
Muktol

When using Krenko there are some cards you could take a look at. I will try to keep it budget-friendly as this seems to be the goal of this deck. Also a short deck description and how to play would be nice.

Goblin Bushwhacker (~0,6$/card), Goblin Wardriver (~0,4$/card), Mogg War Marshal (0,5$/card), Goblin Grenade (~1$/card), Quest for the Goblin Lord (~0,5$/card), Magewright's Stone (~0,7$/card)

Greetings
Muktol

Another option would be to built a B/W standard legal lifeleech/ lfegain deck. I've been working on one (http://www.mtgvault.com/muktol/decks/standard-life-gain/) but it's still under construction so the help it might provide is limited.

Some further suggestions I found after a quick search:
Brutal Hordechief, Foul-Tongue Shriek, Kalastria Healer, Retreat to Hagra, Suffer the Past, Syphon Life

http://www.mtgcommander.net/rules.php Still no "Conspiracy" on it ;)
There also might be a misunderstanding. The card "Conspiracy" has nothing to do with the conspiracy set released by WotC (http://www.mtgvault.com/cards/search/?q=&searchtype=name&ps=20&s=CNS)

Then welcome to the world of magic! Experience will come as you see other decks, play against unfamiliar decks, talk with people about your decks and so on. The most important thing is having fun, the second one is playing enough. (Sadly I built more decks than I could test at the moment but perhaps better times will come ;) )

You might be interested in http://www.mtgvault.com/muktol/decks/how-to-build-a-deck/. This is a basic description on how to built a deck, do's and dont's and so on.

Basically there are many ways of building a vampire deck: Combo (mostly liegain/ lifeleech), aggro with a big part of control, mid-/ lategame different colors and so on. The basic idea about building a deck is having a strategy and stick with it (As you might allready have read in the 'how to' link I provided above). Mixing strategies is a not so good decision most of the times. Remember that your deck can't be good against every deck and that you have a sideboard where cards taht you feel that you could use against decks you are weak against should go.

'Lifelink-based aggression'...with the new zendikar expansion came some cards that benefit from lifegain: Bloodbond Vampire, Defiant Bloodlord but most of those benefit from quantity in lifegain rather than quality (1+1+1>3). The basic question at the moment: Is "Vampire Nighthawk" enough lifegain? Because that's your only creature with lifelink. "Blood Artist" can produce some life but for that something must die, "Sorin Markov" can to but he's in the deck only once, so the chances of drawing him are rather low without tutors or carddraw.
If you want to built this as a vampire lifegain deck I would re-think the card choices. What I would do at the moment is clone this deck, so that I have one to play around with and one that resembles the status quo. If you finish one of the decks you can either leave the other as it is or start rebuilding it.

Conspiracy isn't on the official banlist (http://magic.wizards.com/en/gameinfo/gameplay/formats/commander) so it's legal to use in commander.

*like*
When using Krenko in a U/R deck I would take a look at "Intruder Alarm". I would remove "Chromatic Lantern" and add some duallands instead. This will raise the costs of the deck a little bit but in the end you will get a faster and more stable deck.
"Mogg War Marshal" or "Goblin Chieftain" might be an option instead of "Krenko's Enforcer". The Marshal gives you an additional token while the Chieftain provides +1/+1 and haste for all other goblins.

Greetins
Muktol

I would try to lower the mana-curve of this deck a little bit. Basically (without acceleration) you will be able to play a land every turn for the first 3 turns. After that you will be able to play an addition land ever 2-3 turns. So putting so many expensive spells into a deck will slow your play down.
When using mid to lategame creatures and spells you will need a lot of control over your opponent: Discard, destroy creatures and so on. So try to focus on 1-2 finishers, fill the rest with good creatures and control cards. You might also want to put some tutors or carddraw in to make sure you get the finishers when you need them.

Some suggestions based on my own monoB vampire deck (http://www.mtgvault.com/muktol/decks/vampire-onslaught-revised/)
Gatekeeper of Malakir, Viscera Seer, Vampire Lacerator (more for aggressive decks), Pulse Tracker
Go for the Throat, Tragic Slip, Doom Blade, Duress, Distress, Evil Presence
Blade of the Bloodchief

Greetings
Muktol

Thank you for your suggestion.
The warrior-'tribe' was more an accident than real purpose. Nevertheless I added "Rubblebelt Raiders" to my sideboard and will give them a try if I get to make some testgames.

No, I meant: http://www.mtgvault.com/card/ghostly-prison/CHK/
"Prison Term" can be pretty good, but if you want more control (at higher costs tough) try "Cage of Hands" or "Forced Worship"

Brain must have been away somewhere else while I was looking at "Foundry Street Denizen"