Indeed brah, 'tis most difficult to make a competitive deck for less than $100 in this format. But agreeably, Reshiphlosion is probably the cheapest and best you can build for your price range. If you can find HGSS starter kits, those are your best shots to get pokemon collectors that you'll need to have the competitive edge. The collectors themselves are worth more than the kit itself, plus you get a pack, so it's an epic win. Typhlosion Prime tins are scarce, but not impossible to find. Stores in my area like Kmart and Meijer tend to have a few floating around. Reshiram tins you can find anywhere.
Your deck should come out looking something like this:
3-2-3 Typhlosion Prime(HGSS/HGSS(Promo))(Cyndaquils(HGSS-60HP Prevents Yanmega snipes)
4 Reshiram(BW)
2-2 Ninetales(HGSS/COL)(Vulpix(UL-More HP and a more useful attack if in a jam))
1 to 2 Cleffa/Tyrogue(Optional-Cleffa helps Cycle hands and stall, Tyroge can KO Cleffas and do damage and stall)*
12(Fire)Energy
3 to 4 Pokemon Collector(HGSS)
2 Professor Oak's New Theory/Professor Juniper(HGSS/COL,BW(Personal preference. Oak shuffles into a new hand, Juniper discards into a new hand))
2 to 3* Professor Elm's Training Method(HGSS/COL)
2 Sage's Training/Engineer's Adjustments/Cheren(UD/COL,UL,EP(Sage's lets you see 5, pick 2 and discard the rest, so it's pretty good overall. Engineer's lets you draw 4, but you have to have an energy. Cheren just lets you draw 3, which is slightly better than Bill, but slightly worse than Engineer's, but there's no cost to draw.))
3 to 4 Junk Arms(Triumphant)
3 Pluspower(HGSS/BW)
2 to 3* Rare Candy(UL)
1 Revive(BW)
1 to 2 Pokemon Catcher(EP)*
1 Max Potion(EP)
1 to 2* Energy Retrieval(BW)
2 to 3 Pokemon Communication(HGSS/BW)
Look over this list and look up the prices online. This should give you a better understanding of what you need and what you can play around with to tweak and make the deck better.
* Towards the end of a card means its priority in the deck is lower. * Next to a number means that you should at least have the lower number of the card in the deck, but no less.