Harem
1. Lucy Heartfilia
2. Erza Scarlet
3. Mirajane Strauss
4. Wendy Marvell
5. Irene Belserion
6. Ultear Milkovich
7. Cana Alberona
8. Mavis Vermillion
Although, this is the final list I could maybe as the story progresses change or replace but the number most likely won't increase.
I am not sure if I should add Lucy to the harem because I think she will be better with Natsu and this will keep the story interesting. As throughout the canon, there has been hardly any romance shown with characters such as Erza, Mirajane, and Wendy. Let me know in the comment below.