Abs wheel rollouts are definitely fine and as stated above you can use the rings for the same. L-sit /V-sit/manna variation is good too. With gymnastics type stuff you'll be getting core work through that anyway.
Ross' books are good as well.
Obviously, weights for lower body. KBs are good. Sprinting is great. WOrk on pistols as well.
Gymnastics strength stuff depends on your goals. My book would definitely be able to help you with whatever direction you wanted to go for that.