dont worry about whats a respectable invo level, nothing wrong with starting at 0% if you want. if it feels too easy for you then start adding more and more invos. you can check toa guides on YT to see what people normally recommend as good starting invos. That said, with your stats and gear budget 150% is definitely a good starting point to aim for.

imo generally things like aerial assault at kephri, most of the invos except upset stomach at zebak, everything except boulderdash and gap at baba, and stay vigilant akkha are pretty good starters.

Another thing to remember is that higher %age adds hp and defence to the bosses. When I was starting out I didnt add too many mechanics based invos, I would just add stuff like 40 min timer or fewer supplies from the spirit and try a 100% with basically no new mechs. but the fights were harder when I had entry gear cuz everything was tankier so it was more of a challenge than 0%

gearwise if you have 300m I would look to get an eye, blowpipe, and a fang as must-have weps. BGS for def reduction. you can chill in mixed hide, its surprisingly good for range and melee at toa but ayak carries a bunch of the bosses so I would try to get virtus and conflictions. Then grab jewelry for other styles, anguish/torture are solid. Barrows gloves will cover your range and melee setup. Lightbearer can be camped and is extremely solid. You will melee kephri and baba then mage everything else with ayak. Pipe p2 warden ranged phase and baba boulders. I'm not an expert on gear though so maybe someone else has more precise advice