Been playing Willo casually on and off since 2019. I am a mid-level player, so this build is centered around dominating mid-ranked/casual siege and TDM/Onslaught.
Sprouts and Just Believe are essential to keeping areas locked down with your massive AOE abilities. I like going for crazy cooldown resets, so both of these cards are pretty high on the list. If you feel like you're going to be locked down easily, feel free to take some resources out of Sprouts and put them into Flora and Spritely.
Increase the damage of each Seedling to 750 and reduce the time it takes for them to explode by 25%.
Reduce the Cooldown of Seedling by 2.5s for each enemy hit by it.
Reduce your active Cooldowns by 32% after getting an Elimination.
Increase your maximum Health by 150.
Reduce your damage taken by 10% for 3s after activating Flutter.
Generate 1 Ammo after activating Flutter.
Reduce the Damage you take from Direct and Area of Effect attacks by 6%.
Gain 7% Movement Speed.
Reduce the Cooldown of all your abilities by 10%.
Increase your base maximum Health by 5.5%.
The Haven + Nimble start is great for surviving dive early and lets you live and maneuver long enough to push your ability spam onto the objective. Going immediately into Chronos lets you chuck more seeds, deny more healing and stack DR with Spritely. If you're struggling, go Veteran to just tank that shit out. Also, like Illuminate and Resilience when you need them obviously.
People with low or telegraphed mobility can get choked by seedlings. Also, anyone with a big hitbox to get Sprouts resets. I'm gonna include most frontlines other than the ones I included because they don't have a shield to block sprouts because all tanks hate dead zone.
Most of my build prioritizes some sort of defense for a reason, she is very susceptible to high burst dive if caught without cooldowns. Fliers, Hitscans, and anything with high mobility or range can easily shut her down if you get too greedy. Characters like Terminus that benefit from spam can be annoying too, so be sure to play carefully with your cooldowns around him.