generally, Gina is a somewhat hard to use unit as most of the time you can fare just as well with a 2nd soldier or an archer to support your 1st soldier (katie) for early rushes.

as usual, the general idea is to get 50cc30 with 100% affection for the following:
Katie = bashira = iris = cloris (only if you're rushing to phalanx 2, otherwise she is lower priority) > bernice/leeanne = soma/daniela =alissa > cloris/calliope = valerie = leeanne/2nd heavy

in this case, Victoria can temporarily replace the need to get a Spica, but you will likely lack silver archers to CC her, so just use bashira + Soma/Daniela for now. then Bernice and leeanne will suffice for most tanking. adele replaces cloris and yuyu replaces calliope although you will want a mincosted calliope in the future. Camilla replaces Iris and Iris replaces Alissa, but you'll probably want a 3rd healer anyway later on, which alissa can be. Cyrus can replace valerie.

After the core team I mentioned above, you'll want gankers and duelists, which include Lilia, Gina and Elaine for you. and Eunice/Conrad/Cypria. Marle and Zola should be low priority for now as they'll be harder to use as compared to the others.
and 1 team of 15 units is never enough to cover all grounds for event purposes. check out lafate's unit composition guide, he listed a recommended team composition there.