I can give you some pointers:
H+K is good if you've already got the opponent in stun. Limbo stun gives a guaranteed 7K and afterwards you can do the same amount of juggles as in a CB combo (gives same launch height). So I think it's a good tool overall.
66K is nice. It's a whiff punisher, it's safe and it gives a crumple stun which you cannot slow escape. One of Marie's best ranged tools.
BT 2K is good in some situations. Unsafe but crushes mids like crazy.
4PK gives two stuns on Normal Hit. Semi-safe but I get away with it most of the time.
9K and 9K4 give a stun on Normal Hit. Also: Safe and crushes lows. 9K4 allows for more mix-ups.
6P+K also gives a stun on Normal Hit. You have a lot of options from here. You can go into Rondo or Minuet for many mix-ups. It's safe as well.
3H+K covers great distance and stuns on Normal Hit. Disadvantage: The move is unsafe on block.
P+K crushes lows. Safe and has 236P (Meow) follow-up on counter hit.
236P (Meow) is great as a wall splat, especially when there's some space between you and the opponent. Use it sparingly though, it's unsafe on block.
BT OH is a no-brainer and should be in everyone's Marie play. Gets you a guaranteed 8K launch with PPP > PP6PK follow-up. Or you can go for the mindgame with the the almost endless amount of options she has.
3P is a good lift stun. Is guaranteed after KK sit-down or 64P sit-down. Has a delayable kick follow-up too.
4P+K Rondo Parry works well against punch-heavy characters (e.g. Gen Fu or Christie)
BT H+K is one of your main juggles. On block it's safe and the guard pressure is huge for your opponent. Blockstun is big so almost impossible to hold the second part of the animation.
Overall, I tend to use Marie's safe moves and moves which stun on Normal Hit so you don't have to rely on counter hits. She is a great character imo, aside from the lack of efficiency when played beyond close range.