My 2 cents
Protien powder; If you diet needs a boost in that regard or for conveiniance sake. Bigger you get more you'll probably need powders to get in kcakl and protein demands. A decent whey will do. Prefferably from a good 'bulk' supplier to keep cost down.
Pre-wo; I think these type products are rarely needed. Many use ingrediants that are of no real use or not even needed in a pre-wo product eg creatine and beta-alanine. Or use a 'propiretry blend' that are under dosed. Maybe worth having on occassion. I'd rather just stick to a cup of coffee or even just a can of coke. Diet or not (depenent if I felt I needed the sugar?).
Creatine; A solid product and worth taking. Get creatine mono from a decent company, and job done.
Sweat and pain; No1 ingrediants for happy lifting
Multi-vits; If you think your diet is bad in this regard and you need an extra broad range of vits. Prob worth looking for a decent product if thats the case.
Fish oils et al; Probably a good thing. If I was going to use I'd, again, shop for a quality product.
As can be seen loads depends on your diet.