Hmm, I usually just use 66B BE as a normal attack, I'm not sure how I could use it as a part of a combo?
I can't use GI yet, and I'm not sure if it's even worth practicing a lot since it's even harder pulling it off online.
Yes, this is another move that I use often, but it feels a bit slow and I'm not sure what I'm supposed to do if it gets blocked. If it does hit, then I'm able to continue with 4k and/or 1k which is great.
I really got to work on my spacing game and blocking in general, I'm blocking lows way too often nowadays...I'm not sure but it might be the fact that I've been playing Street Fighter and got used to the fact that low blocks pretty much everything there xD
Well I can't say for sure as I still haven't played that much against different characters since 50% of online players are Natsus while the rest mainly consist of characters like Mitsurugi and Nightmare I guess. It's just players that like to be very aggressive, running towards me all the time and using their fast/long range attacks and/or throws before I get the chance to respond.
66B BE is disasterous as a normal attack against anyone who knows how to just guard (same with 236AA BE). The 2nd hit is really easy to just guard. Alternatively, the 2nd hit can be stepped and there's a number of evasive moves that will dodge it as well. But, if your opponent doesn't demonstrate knowledge of how to deal with it, feel free to abuse it.
Combo wise, 4B 66B BE 22BAK is good. 22A 66B BE and CH 1K 66B BE are good too (especially if they try to tech, it'll launch them).
Its also just generally good against people who try to roll around, though somewhat risky if they stand up instead.
GI's are definitely worth practicing. GI into 236B:4 is really good damage for the meter expended. Just as a get out of a mixup free card, its great. You should also practice using her free A+B auto-gi against strings with mids in them. Don't waste meter on a GI when A+B can do it for free with the bonus of not being re-GI'able. And don't waste meter on a string when you can JG it and get a bit of free meter and a guaranteed punish.
If you hit with 22K, don't do 4K or 1K, you want to do: 22K 236B:4, it'll be far more damaging.
Blocking low without a purpose is a bad idea in general in this game. The really good and damaging moves almost all tend to be mids. The fast lows tend to just be light pokes, and the slower knockdown lows that you care about being hit by are fairly reactable. If I think someone is going to do a high/throw against me, I tend to prefer guessing with a TC move (3A+B, 6B+K, 66A) as that has a chance of interrupting a slower mid/low as well. Similarly with low/throw, TJ moves are good there (8K, 8B).
Natsu doesn't have too much in the way of range. Backdashing and 44B/44A tend to work well against her. Nightmare, is bad news for you, but, watch the Pyrrha vs Nightmare punishment video. It is annoying that only a small handfull of characters tend to ever be used online.
You can always practice the other matchups some against the cpu, that will at least teach you to react to some of their moveset (not necessarily the best parts of it) and let you practice blocking/punishing/JG'ing/GI'ing. I'll sometimes practice against it with the goal of only attacking back when guaranteed to do so (be it a whiff, JG, step, etc).