25 weeks pregnant with anterior placenta. How much fetal movement should I be feeling?

Cannot answer well. Anterior placenta may interfere with you feeling your fetus as well as someone whose placenta is not anterior . You should still appreciate some movements.
Atleast. 4 movements in an hour or 10 in 2 hours. You may experience much more than that with varying intensity and frequency. Often you may not, this is due to fetal sleep cycle.