Quote from NoNeedToBragoBoutIt »Precons certainly are good options to get into the game on a tight budget.
Aside from that, playing mono colored decks can help a lot - with the exception of some and staples.
In a casual enviroment like yours there are plenty of options if you feel like building the deck yourself. You'll need a well sorted store and/or friends with extensive collections nearby though, because my experience with budgets builds is, that if you have to order the cards online shipping will consume a large chump of your already small budget.
's Danitha Capashen, Paragon, Kemba, Kha Regent, Sram, Senior Edificer and Teshar, Ancestor's Apostle leave enough design space, to build them with cheap-ish cards.
has Talrand, Sky Summoner who is considerably strong as long as you keep the curve as low as possible, no matter the single card cost. Azami, Lady of Scrolls doesn't take too much money and effort either, since WotC overprinted Wizards massively.
is a little trickier, as most major strategies and staples get relatively pricy fast. Toshiro Umezawa and Balthor the Defiled may be affordable options.
has my favorite budget commander: Zada, Hedron Grinder! The avg. card price of that deck is laughably low and it works very decently without the money cards in color. Grenzo, Havoc Raiser and Valduk, Keeper of the Flame should be fun, too.
In you have Yeva, Nature's Herald, who allows you to play virtually any creatures you have available. Yisan, the Wanderer Bard allows you to do the same and can become a beast with latter upgrades. Goreclaw, Terror of Qal Sisma and Surrak, the Hunt Caller can bring out the Timmy in you.
I'm curious to see what you'll end up with and happily offer advice.
I'd say zada too. Cheap, maybe a little glass cannon, but effective.
Stay with as few color as you can.