Hi @inspiringgirl, I have been working with clients of varying abilities for the last 10 years and have tried numerous variations of exercises and routines to work on the three areas that you are talking about.
From all of my observations and feedback a lot of the new techniques that promise amazing results do not hold a candle to the tried and tested methods.
Legs and Glutes
Basic compound movements are always going to provide the most stimulation. Squats, lunges, stiff leg deadlifts and hip thrusts in all of their varieties will absolutely be the most beneficial. Add in a few isolation exercises like leg curls, extensions and Bulgarian split squats and you'll be set. When in doubt Google and YouTube are great. Brett Contreras is known as the glute man. I would start there.
Abs
These are much the same. Leg raises and exercises that require resistance are always going to be of more benefit than the high rep ranges often used to perform crunches. There are some great ab circuits getting around the internet. Check them out and mix and match. The important thing to remember is to avoid doing to much oblique work. We all want those sharp obliques but too many twists and side crunches will only make your waist bigger and thicker.
Hope this helped.
G