Alright for PvE, you can't go wrong with a STR/DEX build, maybe try a quality build with 40/40 STR/DEX. I used a quality build for my 1st play through and I never had too much trouble. Just use refined infusion (sometimes sharp, like LKGS has higher damage on sharp that refined, and it can be buffed for some damn nice damage), and buff as necessary for certain bosses/enemies and whatnot. An INT/FTH build is also pretty good with chaos/dark infusions, but certain enemies/bosses have resistances to fire/dark damage that might make PvE a bit harder. I don't know about blessed infusion being any good, sorry bud. For PvP, any build is fine, as long as you know your weapon, use the right infusions, and are decent at fighting other people. I suggest you try PvP and respec with Rosaria to try different builds to see which one suits you. Anyway, hope my comment helps you. Have fun!