So this is a project I wanted to engage in- To make a set of 10+ super-budget 60-card decks that are simple, relatively easy to play, relatively easy to understand, and bring across the fundamentals of how Magic Works. We've since gone way past 10, with tons more in the works, and I've really enjoyed the challenge of trying to make these decks easy to play and understand, fun, and all under a $15 budget, sideboard included.
The main goal here is that you could easily build these deck for a low cost and use them as an easy introduction to how magic works, to teach a group of new players both how to play, and give them a sense of Why, a sense of what fun things they're getting into. These decks aren't gonna be particularly good, or even legal in any particular format if it stops me from including a card I think is good for the deck, but they should be fun and interesting without being too hard to get into. They should be an easily-accessible example of how fun Magic: The Gathering can be.
This is one of the more advanced decks- Not even because it's more mechanically complex, but because it's not the impression you want to leave people with about what control decks are supposed to be- the lack of card advantage and reliance on an artifact is a bit weird, and you probably don't want this to be one of the first decks people play.
This one's a bit of a mess. The good news is that there was actually a pretty sweet Boros Angel I was able to use, despite the fact that I've been avoiding legendaries in these decks (Legend Rule is a complication explained nowhere on the card that feels bad, also they're all more expensive than they should be because rarity and Commander), but the bad news is that control decks that can't draw cards kinda suck. Particularly because Any other way you get card advantage is usually a commander-playable 2-for-1, and thus is expensive. So I play Sunset Pyramid, which is actually not terrible as far as colorless card draw goes (2nd place goes to Hedron Archive, and 3rd to Jayemdae Tome in the Sideboard there), it just kinda feels bad.
The real upside is that I'm probably going to make a Jeskai version of this deck that will be way better, even though it'll probably cut Rorix Bladewing to avoid that triple-red mana cost.
For budget- Maindeck cost is currently at ~$11 (according to the middle blue numbers on this very site under estimated value), sideboard at about ~$3.20, which gets us nicely under out $15 limit, despite those damn overcosted Rorix Bladewings. You might save a respectable amount of change if you swap 'em for normal Shivan Dragons.
So mostly this section is going to be notes on why I think these are good cards to learn from:
Firemane Angel Ain't Baneslayer, but she'll do. Also 10 mana just brings it back unless it's exiled, which is way overcosted, but kinda sweet, also something something incidental lifegain. It's understated for a 6-drop, but that's fine. The dragon makes up for it.
Serra Angel is a classic that I love throwing in these decks because it's actually a great way to learn how vigilance works, and is just a cool angel card that feels like a reward for playing a control deck. You didn't get to do anything for the early turns but defend yourself, and now you get to play this sweet angel to kill them with.
Speaking of rewards for playing a control deck- Rorix Bladewing, where have you been all my life? Seriously, this is the first time I've ever seen this card, and it's freakin' sweet. A 6 power 6-drop with haste and flying is a monster of a win condition, and what with it being a big sweet dragon on top of that, it]s going to be a huge hit with new players like these decks are intended for. It's cards like this that are why I don't limit myself to modern-legal cards. That, and the odd hilarious commander or Conspiracy card. Edit: God damnit, it's Legendary. I've been trying to avoid them because I don't want to have rules the card never bothers to explain, besides keywords, which some cards explain anyways, but I'm willing to make an exception here- Rorix Bladewing is a sweet card, and you don't really need more than one to stick around. I'll lower the density a little, but it's probably the most reasonable way to teach the Legend Rule.
Your boardwipes are Planar Outburst and Slagstorm, both relatively simple, both quite powerful, and both really good at what they do.
To keep you alive between boardwipes, we have a suite of (mostly white) removal classics- Immolating Glare, Reprisal, Searing Spear, Banishing Light and Pacifism. I had Warleader's Helix in here for awhile, because 4 damage is real good and the lifegain is respectable, but cut it for pacifism to cut the price a little. You could bring them back and still be under-budget, but I kinda like the removal cheaper, even if the lifegain can be relevant. Inferno Trap was a later addition that I like, because the alt casting cost is a good lesson, and learning the fact that Flame Slash is real good is a nifty lesson.
Your only card advantage is Sunset Pyramid- It's 8 mana to draw 3, but split over turns, and all but the first 2 mana invested is at instant speed, so you can hold up mana for removal and choose to draw or not. I would play most any real card draw spell in the game first, but in Boros, you work with the tools provided to you.
Manabase is meant to be a touch lacking, but also super-budget. I'll be doing the same for all of them.
As for the sideboard, this IS supposed to be a sideboard they learn how to use, to make their deck perform better in the right matchups, or just in general to customize their decks within constraints.
I went with Aerial Responder here as an anti-agro card, getting you on the board early and gaining you some life, even if it dies to baordwipes. Extra Serra Angel and Rorix Bladewing for adding to your threat density, and I decided to go with 2 copies of pyroclasm instead of an extra Planar Outburst and Slagstorm. It's faster against a lot of agro decks, and easier on the budget, though I think you could replace them with Outburst and Slagstorm and still be fine.
Revoke Essence is good artifact/enchantment hate, puncturing light and reprisal are the only sideboard removal spells that stuck around, but are also among the more situational. And the unspellable tome is your second-best option for colorless card advantage. Believe me, I tried looking for Boros card draw, there is none to be found. This is why people hate these colors in commander.