Thank you so much!! In all honesty, I can't really tell you a concrete number, but plot-wise you basically will have to get through season 1's plot and find Belphie before you get the option to embark on a route and "lock in" your love interest. Before that, you can basically romance anyone you like and build intimacy with them :) and you will be able to choose routes for every character that you have enough intimacy with! (And to get intimacy, you'll have plenty of opportunities to hang out with the LIs and get closer ^^)