Wario is a matchup where you really have to buckle down and commit yourself to bair spam. Wario's poor range on his aerials means the vines stifle him heavily. He also doesn't have projectiles, so use full jumped razor leafs to control areas both in the air and on the ground, but watch out for Wario air dodges, since his mobility enables him to use them effectively closing gaps. On the ground, Wario has very little to get past ftilt, other than his super armored fsmash. In my experience, Ivysaur's reach is very difficult for Wario, who apart from not having half the reach she does, doesn't have the priority on his attacks to cut through defenses. Remembering that Wario can't auto-sweetspot the ledge with his recovery is important, since if you see the opponent is trying to manually sweetspot, you can go for a quick edgehog, which Ivy is good at. If the overshoot the ledge, use dtilt or fsmash to get them off. Another good thing to watch out for is when they recover high with the bike, you can easily position yourself for a sweetspotted vine whip once they do their initial dismount, which has some frames in which Wario cannot air dodge.
Now that we're on the topic of committing to bair spam, it's really essential in order to play Ivysaur that you never shy away from spamming bair if it is working. However, bair spam works less effectively on some specifiv characters with quick, high priority counters fast enough to get to you between bairs (Snakes, for instance will dash attack cancel out of their shield if you miss a step, or they can ftilt if you mess up your zoning by even a bit). Because of this, it's important to practice your bair spam so that you reduce the time between bairs to a minimum (always start it up as soon as you SH and always fast fall), and learn to watch the opponent for signs of their next move, to decide when to keep spamming the move, when to turn around and grab or ftilt, or when to retreat.
