My experience has been to go sailing with what you have and let the boat tell you what you need. Also it depends on the style of racing as cans are very different to offshore to cruising setups. You dont need to "trim" the jib like a crewed boat, its a bit more of set and forget unless its light and youre sitting to leeward. Cross sheeting is a pain in the ass. Mainsheet needs to have a central fixed swiveling ratchet with a cam that leads of to your boom/trav setup, ideally this is forward of where youre sitting. If youre doing distance the easiest way to self steering is a tillerpilot/solar panel. You could try bungees/tiller brakes etc but Ive never found them to be that great on a fin keeler. Its pretty easy to set up the vang/cunningham/outhaul to lead back with multiple spectra purchases, low friction rings and cam cleats. I would spend time making the cockpit comfortable with good bum padding, nonskid, footblocks, decluttering etc
Single handed you are never going to go as well as a crewed boat so at least make it work for you, however two handed you dont need to make that many changes. You just need to get out there and make changes in response to what you need.