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.
So this deck's a fun one, and a new version of one of the earliest decks I ever brewed- Selesnya Tokens. You ramp some mana, and then use it and your guildmage to spam Tokens like there's no tomorrow- In this case, Hippos and Centaurs if you have to, but 5/5 Wurms when possible, and you just turn 'em sideways in a big, nasty horde of monsters.
As for budget: Maindeck cost is currently at ~$10 (according to the middle blue numbers on this very site under estimated value), sideboard at about ~$2.50, nicely beneath my $15 limit, once I cut the copies of Armada Wurm.
So mostly this section is going to be notes on why I think these are good cards to learn from:
Druid of the Cowl and Naga Vitalist are nice ramp creatures. You can swap them out for, say, Avacyn's Pilgrim and Llanowar Elves if you want to, I wouldn't begrudge you that, but I felt like making the teaching decks lean toward what's become the norm for mana dorks, ie 2-drops that are still good, but not as good as the 1-drop mana dorks.
Your prime token Generators are Mouth // Feed, Call of the Conclave, and Advent of the Wurm, providing functionally identical 3/3s in the two former cases, and sweet 5/5 tramplers in the case of Advent. These are powerful bodies that you're going to use to dominate the board and crash in for sick damage.
And part of how you're going to do that is by making them multiply- Vitu-Ghazi guildmage is a vital part of the deck for its ability to take in mana and spit out extra copies of whatever the nastiest token you've got on the board is. If that's a Wurm, you're golden. If that's a 3/3, hey, 3/3s for 4 with no card disadvantage is still pretty good.
The aftermath half of Mouth//Feed also lets you draw a bunch of cards off of all your tokens, and teaches new players that getting greedy and trying to draw a million cards when you could've just drawn 3 or 4 will loose you games. Also, at your top-end, Courser's Accord lets you drop an extra 3/3 and at worst. a second 3/3, if you're lucky, a 3/3 and a 5/5.
The rest is removal- just like Populate, Pounce is solid with a 3/3, and lethal with a wurm in play, and Reprisal, Pacifism, and banishing light are all just solid, good cards.
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.
Sideboarding was fun in this deck because I got to fully replace Naturalize with Sundering Growth, which I might've put mainboard if you could cast it as just a populate, but since it can only even be cast if you have a target, it's not reliable enough.
Druid's Deliverance and Rootborn defense were also tempting maindeck options, but I always hate cutting removal for toys like this, so I let them slide to the sideboard. You can make a judgement call on that, or let the students make their own judgement calls and figure it out, it's their sideboard.
And the rest is just plummet (which is your only interaction with flying other than normal removal spells) and extra copies of pacifism, pounce and reprisal, for boarding in in place of whatever removal isn't doing much against a given opponent.