There is a choice in 5.0? I may be confused but the only "end" (i.e. back to Title Screen) was with Elena.
The other routes don't lead to an ending because our current saves aren't going to work properly, if at all in 0.5 which lets us explore all paths at this current moment without keeping multiple saves.
So the choice is going to be play the Sera route, the Cecille route, the Elena route, the Erin route, or a little bit of all of them and then pick an ending that will lead to the duel, or in Erin's case bypassing the duel. The last one will probably be the best way to get sex scenes with all 4 LIs and will probably also be the best way to get a good spread of points to put you on the harem path, assuming 0.5 saves carry into the future.