Need some help

In terms of the GT, I'd go with the priciest player at a position of need. Since we can't see your lineup, I can only guess it would be one of Mays, Megatron, White, Polamalu, Bo, or Julio. I wouldn't take a QB since there are budget GT options that are super-effective, but whoever you user on defense would be the way I'd lean. For me, Mays and Julio were the biggest game-changers, but I've seen tons of awesome users with Polamalu and his abilities (lurker/enforcer are a must).

With physical chems, I agree with ch29sk - Brawler and Sprinter are must-haves for playing online at this point. If you have tons of training, putting Brawler on your offensive and defensive line (and any rush LBs) with enough 2x's to hit 30/30 and Sprinter on your skill positions and secondary/coverage LBs with 2x's to hit 30/30 also would be the luxury choice. Personally, I went budget and just but Brawler x1 on everyone and have no complaints.

For scheme chems, it depends on whether you play a ton online or not. If you do, Run Stuff on defense is a must. If not, go with whatever fits your play style - and if you have the training to burn, splitting it up so you can hit 30/30 in two chems each (like, run stuff for your front guys and lockdown for your secondary/coverage LBs) is definitely useful.

The GT is based largely on your needs, but I would definitely take one of the more expensive ones for a position where you don't have a great end game card yet. So maybe if you have maxed captain Shazier and PU Willis, you may not need Troy, otherwise that's a great option. If you have ST or Lott, you may not need Calvin FS, otherwise that's a great option. Same for QB. Also good options are imho Mays, Julio and Bo. So it depends on your team's needs I would say.

As for physical chems - I would say speed kills. I have maxed out both Sprinter and Brawler, if you're able to max just one, I would go with Brawler because fo the physical positions.

Not an expert on O and D schemes, this I will leave to others to discuss.

Sidenote: you haven't really posted the lineup, just the link to the Team builder, so can't tell you a specific answer for the GT.