I've got a bunch of Helena stuff in my guide that should be helpful. It's technically 3.1, but the combos and most of the setups will carry over to 3.0. I also use Tina, so I can help you there, although VP is the expert.
Basic Tina stuff:
- Launch,

,

,

- Basic juggle. You get a free ground throw if the air throw ends near a wall.
- Opponent comes off wall,


,


,

,


, Basic wall combo against lights. For mediums I believe you only do one


, and for heavies I believe you launch with



and then do

,

,

,


.
-


guarantees a ground throw on CH and HCH.
-


gives you a slip stun on any surface that allows it. This allows you to set up a mixup by freestepping using

and looking for a hold. If they hold, you can punish with




since you're already buffering the

for 120 damage or something ridiculous like that. If they don't, you just walk around to their back and get a free BT combo.
There are some match vids of me and VPai using Tina in the media section. There was also a recent FT10 between Gill Hustle and I that got uploaded and I use Helena throughout the whole thing. It was the first time I played DOA in a long time so it's not the best example of Helena play since I'm so rusty, but it would definitely help you pick up the basics. You should also look up anything labeled UGS in the DOA 3 section. That's the offline scene I play with. I don't know what matches I play in so you may have to do some digging, but there are definitely some Tina and Helena sets in there that might help.