Try out chloe ting's workout programs
They are very effective
Plank, JackKnife, Flutter Kicks, Burpees
Push-ups and Crunches are the best (in my opinion) because I've seen the results from it.
Burpees is the best way to loose that extra tire
Planks,crunches, jack knives,leg raises,russian twists can be good starters
Do HIIT, it's really helpful