Oblation and Swords to Plowshare are great removal options that are not too expensive.
Ah sorry, didn't see it until now. I would drop some of the smaller token generators that don't leave a big impact on the board. Patrol Signaler is a fairly weak choice, perhaps gather the townsfolk as well. Judging on the cards in the deck you want big tokens to populate with, so emphasising the bigger tokens are key. Phyrexian Processer is great, Crush of Wurms is also a good card to consider for the deck, Well of Lost Dreams has great synergy with Trostani, it allows you to draw cards as well with the lifegain, which is really nice since a 100 card is a lot of cards to go through especially to get what you need to fight back.(Harmoize is also another cheap budget option you can use to draw cards as well).
Here's a resource that will probably be very beneficial to future tuning of the deck, a lot of great info on tokens. (And oh yeah, Aura Shards is incredible in a token deck).
I know I'm late to the party here but how about Rhox Faithmender Doubles all that nice life gain from trostani.
On the subject of budget, does your friend already have an elesh norn? Because she is worth 15$. Just wanted to point that out. Also how about worldspine wurm? It works fairly well with feed the pack, and especially well if you have parallel lives out. Also maybe consider deaths presence? Since you do sac things, it may be good to have something that could turn their power Into counters.
My friend doesn't have an interest in edh anymore sadly, but if he wants to get back into it I will let him know of the suggestions
i think an Avenger of Zendikar would work really well in this deck