Cross Edge

So far, no one has come forward with proof that you can mess this up. However, I would advise against selling anything until you're in the endgame, alchemizing the higher-end items and familiar with what you need and don't need. You don't need money much in this game, so I'll stress again, don't sell. Most things can be used for alchemy in creating better items and most item you make will automatically become purchasable in the shop, so this shortens things. You do not have to own everything at once; once an item is registered in your encyclopedia (pause menu), it's counted. Make frequent Synth Recipe purchases. When selecting an item, the requirements to make it are displayed; hitting or will rotate through more menus for the item, one of which displays what it turns into when fully upgraded. These achievements will seem to take the bulk of your platinum hunt time.