How to build a multi-colour aggro deck to be more effective against control
You've stated that your card pool is limited, and your ability to buy more cards is even more so.  This restricts specific card advice significantly, so I'm going to give some general advice on the process of tuning the deck.

Running a 3 color deck is difficult, as you've already noticed.  Without some specialized cards which are in many cases quite expensive to obtain, it is hard to be competitive.  Here's what I would do:


Ensure the deck is 60 cards, you can go a little higher if you need to.  In no case should you be anywhere near 80+ cards though!  The more cards you add, the more likely you are to get some really weird mana fluctuations.  It's also difficult to sufficiently randomize a larger deck.
Make sure you have enough land!  For a 3 color deck, I'd want probably 24 land and a couple mana producers.  Upwards of 26 land if you have no other mana producers (artifacts/birds of paradise) to include.
Proxy some dual-lands.  Take 4 swamps and write "Red/Green" on them, take 4 plains and write "green/blue".  They are land that can generate either color as necessary (but only 1 mana a turn from each land).  When you are playing with friends, I think a little proxying is fine, but be sure to let them know about it before hand.  Encourage them to try out a few cool old cards as well!  Just because you didn't spend $2000 in 1996 on cards doesn't mean you shouldn't experience those cards every so often.
As you play the new tuned/proxied deck try to figure out which colors are most important.  Shift things around to try to favor 2 colors, focus the third color on being the "finishing" color.  This will allow you to decrease the mana supply for that third color and will make your deck run smoother.  An example would be just including a few mountains and a couple fireballs.  In other words, try to move your color mix from 40%/30%/30% to 40%/40%/20% or even 50%/40$/10%