I would post 3x per day to increase engagement, but more importantly, since you used FL to get followers who are likely not engaged and some who are fake / ghosts, do a cleanup of the account and remove the following:
1) remove private accounts you're following
2) remove inactive accounts who have not posted in last 30 days
3) remove fake accounts
4) etc.
Once you do that, focus on following super active people. If they don't like/comment, then not worth following and reciprocating.
Calculate engagement rate before vs 1 month after.
I've done this for a few accounts already and my engagement slowly improves month-after-month. Wish there was faster way to improve engagement rate, but this is only way that has worked in addition to high quality content.
