Bulk Citrulline Malate (SNS) and/or Agmatine (SNS), Betaine (SNS), and a powdered drink drink mix of your choice (Crystal Light, etc...).
If you train fed, you don't need BCAA (MRM), but those are available in bulk as well.
Beta Alanine (APS CarnoSyn) and Creatine (Universal Creapure) don't need to be taken PrWO, so as long as you are getting them elsewhere... if not - bulk add those.
Companies in parenthesis had the best value/money last time I purchased - YMMV.
While more expensive - I have recently switched out the powdered drink mix, for Ergonine. I can nix the bulk Creatine and Betaine, better taste, some extras that may help... we'll see.