WHY? SAVE YOUR SELF BEFOR IT'S TO LATE!!
Seriously though, toplane is in a horrible state and one of the most misserable experiences this game has to offer, and that comes from a former toplane main that started in Season 0
If you want to transition into a role that can carry games, jungle and mid are what you're looking at.
But if you really want to go to the desolate island of missery that is toplane, you certainly can bring poppy there, especially vs squishy-dashy type of champs like riven, yasuo or irelia she can be really strong.
Orn imo is the best toplane tank atm, not the easiest one but neither the hardest, so if you like tanks you should give him a try.
If you want carry potential top that isn't that hard to learn, i think trynda and jax are a good start. With sanguin blade, their splitpush gets rather disgusting as long as you avoid getting collapsed on. However, as a support main you should probably have a decent enough read on the macro for that.
Toplane lissandra is also a very underated option, she can easily deal with nearly any matchup with her ranged waveclear and good disenage, while also have good all in once the opponent is poked low and a great setup for ganks.
She also has alot playmakeing potential to transition a lead onto the map, which is where most other toplaners have alot of trouble if they can't just win through mindless splitpush.
As for toplane tips in general:
Since you come from support, i expect your not very experiecned at CSing, so i recommand to practice CSing in the practice tool till it comes naturally, learn how to read minions to anticipate which minions will be focused down first.
At some point, you will CS well while beeing brain afk, which means you can put your attention elswhere in lane to see proper openenings for trades/harras or read your opponents intentions to avoid such things.
One thing that really helps, especially if the matchup is in your favour, is indentifying which creep your opponent will CS next and then you can position closer to that and just smack him with an AA as soon as he goes for the CS. Especially with grasp, that can be some good harras if you pull it off a couple of times.
Another important thing is playing around CDs, but that's the case in every lane.
As for overall tradeing, that's mostly an experience thing. Over time, you will get a feel for how much damage you and your opponent are capable off and mostly at what lvls/items the powerspikes of you/your opponent kick in. Many people get confused when they dominate a matchup for some levels and then suddenly get smashed. The most common spikes for toplaners are tiamat, sheen, phage and the first complete item.
Then there is the lvl 3 spike(lvl 2 for some) and obviously lvl 6.
One of the best examples for such a spike is Irelia. She synergieses well with sheen, and her ult is a very powerfull spike, so many irelias play on the backfoot early on, and once the get sheen at lvl 6/7 they suddenly all in you 100-0 cause they get a massive power spike from both lvl and item at roughly the same time.