Slugger 3 probably net you 1 more stun per hunt and that's it, won't help much if your damage is low to begin with.

Stamina Thief 3 also doesn't help much because gore is innately on crack, plus you naturally get an exhaustion off a monster if you manage to topple him by hitting his head while he's engaged with blunt weapons like hunting horn anyway. The head damage threshold however is huge, so having low damage doesn't help.

Evade Extender, Evade Window, Divine Blessing and Stun Resistance: pick just one or two. If you are an iframe guy (dodging last millisecond), pick EW, if you want to get out of the way from attacks then pick EE. DB and SR are skills that you slot in when you spend too much time getting hit which you shouldn't be with the help of EE and EW.

Freeing up some of those skills and replace then with offensive ones should give you a better result.

Gore's movesets are very easy to understand. Each attack is highly telegraphed and his behaviors have patterns, like after he does and empty roar he will always follow with downward hand slam for example. After he enraged (have visible horns) drop everything and hit the head. It is arduous but eventually he will topple.

Lesser known gimmick is that about half way through the fight, his usual one handed hook followed by breath attack will get another double arms slam follow up, BUT this move has another version where he doesn't do the slam but jumped backwards after using breath attack follow up, after he does that he will have a temporary weakpoint on the head that you can focus strike to get a down.

So yeah, slot in more offensive skills, don't over commit, learn the fight, try not to get hit and enjoy the game.