How can I modify Green Tron to better combat Aggro Spirits?
Disclaimer: not an expert on Modern. The following comes from my understanding of other formats &amp; my reading of Modern strategy articles.

As Hall-of-Famer Paulo Vitor Damo Da Rosa wrote, Tron is slightly favoured against spirits, especially pre-board. However, your build of Tron is subpar because your payoff cards are less than ideal. Cards like It That Betrays cost so much mana to cast, doesn't immediately impact the board, and even if you survive to attack with it, you might not win (opponent can sacrifice 2 lands and swing back for lethal). You're also running cards like Nature's Claim in the maindeck, which is completely dead against spirits (this is the reason why Nature's Claim is a sideboard card: it's dead against too many strategies; you only bring it in when it's good). As a result, a complete answer would be very big indeed since it'd involve a complete rebuilding of your deck. I'll refer you instead to these two primers on G/X Tron and Eldrazi Tron on MTG Salvation. Note they are different decks and play out differently - you should choose one and build that way, not try to be both.

For cards themselves I'll mention only these, because they're the most critical to the matchup when both decks are well-built.

Oblivion Stone: I see you're already running four, so you should know how good they are.

Wurmcoil Engine: gaining 6 life means they can't kill you, and it's too powerful for them to trade with. They basically need to have Path to Exile or lose.

Ugin, the Spirit Dragon: Ugin's second ability is a one-sided sweeper against Spirits.

Walking Ballista: this lets you snipe off all their X/1's easily and still maybe have a body left over. Remember it also instantly kills Phantasmal Image.

Edit: remembered that spirits runs Aether Vial, so maindeck Nature's Claim aren't dead. However, it's still not worth it. They will have hands which don't contain Vial, and it's not like you auto-win if they don't have Vial either. Nature's Claim is for fighting the likes of Stony Silence (which, if it resolves, almost paralyzes you) and Affinty; the sideboard is the place for these narrow hate cards, not the maindeck.