Starting to workout, or getting back into it can be a hard thing to do, so I am here to give you my recommendation on how to get that going, and that is T25 from Shaun T and Beachbody. It is a great cardio workout that is only 25 minutes long and will shred your abs if that's what you're looking for (and who isn't?). I personally no longer do T25, but I still mix in a lot of the exercises into my punching bag routine.
The thing I really love about all Shaun T workouts is the modifier aspect of it, which is a lower impact/easier to do version of the move, which lets people slowly work into the program without killing themselves.
The other great aspect about T25 is the fact that all you need is resistance bands and floor space to do it, which keeps the cost down a lot.
If you're thinking about doing it and want a highly in-depth review check out Dumbbells and Diapers'