Hi! I'm a Gold II Poppy main in Brazilian servers, I recently came back into playing ranked but I've been playing League since start of Season 3. Poppy was one of the first champs I bought and the most I loved, I love simple mechanics and tank roles in games and Poppy's personality just pulled me even more, before I came back into ranked and learned all these new Runes, Items and Metas I changed a lot in the way I play Poppy, but honestly the best way to play a champion is your own way! So take this guide as a clearing path on what you can do with her.

I started playing ranked on start of season 3 through the end of season 6, I took a long break til' the end of season 9 and Poppy wouldn't come to be that fun at Top for me anymore, so I tried her Jungle, and then Support, and it was so much better. Poppy Top is definitely decent even now but you can make use of her kit so much more in the jungle or support.

Putting pressure
This is something I mostly do in jungle overall, putting pressure in lanes and objectives is the key to ensure their claim, and as a jungler you're the fittest to make calls so you'll have to be the most communicative in your team. Poppy is a dead simple champion, enemy next to wall = stun, so tell your laners to force their opponents to fight next to walls, most notably in the bushes so the ganks can be better followed.
When claiming dragons, barons and heralds always make sure the enemy jungler is: dead, pretty far or you guarantee to blast him away with your ult when they come, her ult is the best if you wanna ensure epic monsters (also always bring lens or a control ward so you're not spotted when taking them).

Summoning and fighting Heralds
Summoning heralds is the same for every jungler, don't summon it before you know that: if other laners are coming to counter it and if you are sure it can take at least 1 turret, but when fighting against heralds her ult is the perfect counter, just blast it away so you gain time for your teammates to come and take it out before it demolishes a tower or two.

Setting up ganks and when to farm
Before making ganks it's crucial you clear up enemy wards with lens and pink wards and communicate with your team if the enemy is being too passive and attentive, if you see an enemy lane being too agressive and careless make sure you always be nearby, Poppy has heavy early ganks just like Lee Sin so after you make your entire first jungle clear be very active in ganks.

Support
Sup Poppy plays out even simpler, if you see an opportunity to trade with the enemy ADC or Sup, stun them on to the wall and block them with your W if they got a dash, don't let your Shoulderguards charges idling, collect them as fast as you can so you can ward for your team, and always protect your carries if anyone gets anywhere near them.