General:
Haha yeah that was the first thing I was going to say. 66:B believe it or not, not an amazing move outside of punishment and combos. If you get it on CH, you don't get damage + mixups you have to choose (2A+B236B for damage, 1B for mixups). On normal hit it's great, but the real problem is on block. It does bad gauge damage, and moves you much closer to your opponent at -12. Basically it hands them a mixup. And it's really linear, and has zero evasive properties. You did amazing work with it considering what with GI'ing after but it was overused IMHO. Save it mostly for punishment, combos, and maybe interrupting at a distance. If you are frustrated because he's poking you at a distance and you can't poke back with A+B cause it doesn't reach, consider 236A+B, 66K, 1(K). 236B.
Voldo doesn't have a ton of good horizontals. Facing forward, I use AA, 2A, 4A (amazing move), 66(A) if you're feeling brave, 3A if you aren't getting punished for it, that's it. 1A is junk by the way, wouldn't use it so much esp when Ivy loves her 9B or whatever it is. In BS, you have BS 1A, BS AA, 66A (awesome step catch but punishable), BS 6A (not the easiest move to land but it's i14 50+ damage on CH), BS 44 A (effectively replaces 236A+B while in BS), occasionally BS 3A but it's kind of meh.
The overall theme for me with Voldo is pressure. It doesn't mean you always attack, but you should try to make your opponent feel like they don't know what's coming, and that they're being ground down. This is why 66:B is so bad, it doesn't pressure your opponent in any way (except you can try to GI of course, although that can get risky fast).
Mixup pressure: fully nail those A+B (when mixing up) or 66:B (when punishing) combos. Make sure you alternate the just frames to get the maximum number of hits, and then go for 1B. Getting damage AND mixup on these attacks is a major strength of Voldo.
NB: never do 1B if it's not going to pick up. You can tell in advance if it will or not by looking at your opponent. If it's not going to pick up, do the 44(B) ender or 2A+B236G for decent oki, depending on whether you want FF or BS oki.
Gauge pressure: you didn't put hardly any gauge pressure on Ivy at all. 2A+B236A+B is one of my standard early game ploys to see how they take it. If they just block and poke back, I do it again. Literally this only has to go back and forth 3-4 times to get their gauge red. If you had used more 2A+B, A+B, 236A+B instead of 66:B he would have had gauge problems. Also, it's not just about CF'ing, remember that breaking armor gives a damage bonus and Voldo is the best in the business.
Block strings: Instead of just doing 66:B and your offense ending, by doing 2A+B cancels or 4A you can keep attacking and putting pressure on your opponent.
Reverse mixup pressure: Better use of BS A+B. E.g. 1(K) BS A+B = gold. Once they start adapting to that, change your tactics appropriately. Also BS 1A as a reverse mixup. Also, Voldo's step is amazing in BS. Like, one of the best in the game. And the sideways evades (2_8A+K) are amazing in blind stance because they put you in MCHT. Notice that almost his entire reverse mix up game is in BS. Facing forward, you have 4A+K but there aren't a ton of good setups for it, mostly just BB/AA.
So for example, you can do 4A (if blocked) BS AA BS 1A. If they try to interrupt after the 4A, usually the BS AA will hit them at i11, then you can do BS 1A as a mixup. If the BS AA is blocked, you try the BS 1A as a reverse mixup instead relying on the STC frames.
Anti Ivy:
Facing forward, 214B basically evades your entire movelist as it evades to Voldo's weak side and TC's. He hit you with that many times. So there you will have to suck it up and anticipate it, and then punish her for it with 66:B. It's pretty annoying because she can do it not just after her block (more expected) but after you hit her, which really messes up your offense. This is why it's good to be in BS vs Ivy, BS1A and BS 66A work great vs 214B. So you can try 4A for a fast transition into BS at neutral, this gives Ivy problems. You can also do 1(K) more often instead of A+B and see how she reacts. Whiff punish with 236A+B whenever possible. Stay on her like shit on velcro! Once you close distance, do not let her re-open it as long as you are hitting her. If you combo her always sacrifice a little bit of damage if it gives you oki or mixups. You will pay that damage back later with interest trying to get close to her. You can also (this applies vs every character) whore 2A+B cancels against her and see how she reacts. Feel free to use the 236A+G_B+G grabs. They are a good way of creating threat at a distance, and if she steps or evades these moves will often put you in a weird position relative to the other character; they often whiff giving you free damage. Also you'd be amazed how many 236A+G (whiff) BS A+B I will land in a single match.