First of all, Welcome to the forum! You won't find a better bunch, who are more willing to help anywhere.
My suggest, if you just plan to buy another gun for the trigger frame, then sell the rest of the parts, is just to find a used trigger frame. You can find them pretty easily on the B/S/T forums here or on pbnation. Usually they go for about $30-50 used.
As for other upgrades, if you don't already used compressed air, I'd go with that. Really thats the only upgrade that you might find necessary. Well if you get the electronic trigger frame you might also want an anti chop bolt, as well as an electronic loader, if you don't have one already.
Also if you haven't already you might want to check out OtterSC Customs
, he is pretty much the spyder guru and most information that you need to know about spyders are on his site.