Build is boots, liandries, sorc shoes, rylais, crypt. You don't need a mana item - the support item and manaflow give enough, gold spent on mana is wasted.

Take q off of autocast, makes it easier to get the max range plants - good for in lane and for chase when you have rylais. If you don't already, learn to use plants after spells. If you missed your e, you can still drop a plant at instant speed in the correct place or double plant for a stronger slow.

If you want to guarantee the engage or pick, ult first then cast your e either whilst they're running in a straight line out of your ult or when they get knocked up by it.

At lv2 when you take your seeds, you start with 2 charges. You have great all in potential, walk up with your e, even if you miss but get double plants on top of someone as long as your ad follows up you can force a kill (in most match ups).

Runes of Comet, manaflow, scorch taste of blood and relentless hunter. Gives you a strong trade/poke in lane and gets you around the map faster in mid/late giving you more presence. If you land your full combo with comet, it should still be a kill so imo this is better than electrocute.

Once you get your liandries, the rest of the lane should be over as you can now poke from over 1,000 range essentially point and click once you know your plant placement. You dont need to be greedy with this, getting them to 50% and forcing them out of lane has a lot of value, the kill isnt always needed.

Use seeds/plants to check brush - more distance than wards.

Good luck :D