Well Plank, side plank, bridge is something good to start with.
Also hanging leg raises or knee raises helps too. U can also do double crunches , jackknives , sit ups,leg raises etc.
For ur training u can either do super sets or just some sets of some exercises. One super set maybe can be like: 10 hanging leg raises, 10 hanging knee raises , 30 sec plank, 30 sec side plank each side repeat 3 more times (so 4 sets total) with 1-3 min rest between and after than rest 2-3 mins and max out in plank and in side plank in each side.
Hope it helps, this was an example if u want try it by adjusting it to ur level or just make ur own plan with more or less exercises.