You can slightly optimize exp for Ginasta if you want. She always joins the party at lvl 80, and is not beholden to the level of Simon like other party members sometimes have. You can therefore wait to do the Shambling Behemoths from the Order of Silence, the two tower locations from Wendis in the HQ and the lords of stillness/shadow until after the Second Gathering, which will give Ginasta >50k exp extra.
Obviously if you dont do the lord of stillness/shadow you won't have Fheliel in the harem for the Second Gathering, but you can win Nyst event even with only 600 (and I think even 550) mana, so its not that big of a deal.
You can technically wait to do some of these (like order of silence/tower locations) until after you have gathered Lilith after the Incubus War, but Lilith does have her level based on that of Simon, so its better to kill everything before the Incubus War. From what I found (without the EXP shenanigans I posted ages ago about the Erosian Crisis), if you go to Liliths Abode immediately after the Incubus War, and not do anything else, Simon will be level 93 just before you get her.