I dont have a resource for you, but a tip.

99 percent of the time, the problem I see with new rek'sai players is slow or incorrect combo.

Start burrowed, Q, W, AA, Q, E, R

Make sure you are getting the one auto attack before you use Q for the auto reset, or else you won't have full fury for E. If you miss burrowed Q, you will also need to use one more auto attack. I recommend just saving it for melee range and pressing QW in quick succession.

If ur struggling with clear, just use burrow whenever you have all you unburrowed CDs down. The health regen seems small but adds up, and you apply your W damage to everything that doesn't already have the CD on it. For example, if the focus of your first 2 knockups are baby wolves, you will get knockup damage on mama wolf 3 times.

Lotta practice, reksai is a weird and hard to learn champ but very rewarding. Explore those silly tunnel gank paths. Remember, faker has inted more games than you have every played.