This is pretty self explanitory, but I'll give you a little background support. Speaking of support, I'm a support main, and my four big champs are Blitz, Thresh, Janna, and Sona. I can play support fairly well, and I suck at every other role. So who should I try where? What role should I learn how to play first?
Mid-Top-jg-adc since you lie support.
I would try top or jungle next. Since the tank meta is big right now chances are you will play a tank in either position and as a tank your mistakes are more forgiving than if you were a squishy. Top i reccomend Garen Wukong and Malphite jungle i recommend Volibear Vi and Sejuani
Karma's a decent pick for starting as a mage. She has a pretty straight forward kit and her damage early allows you to be a bully. Not to mention her Q has a really low mana cost. (starting cost is literally 50 mana.) She can spam her Q a lot, she is good at engaging and helping with ganks, she can disengage for herself and her jungler/allies if she needs to.
The hardest part about her is that decision making with your Mantra and what you should use, most of the time you will just Mantra Q though.
Even then her passive allows her to easily get her ult off cd really fast. I suggest you check her out.
I would definitely go top or jungle. The nice thing about top is the lane is not as contested as bottom or mid and teaches you to watch out for your own ganks and setup ganks without another in lane. Also, there are a lot of very strong champs that tend to go top that are easy to play. For example, Garen can be very strong especially if you are still learning things.
Jungle, is another great option because you tend to be left alone for awhile, especially in casual low end games where people tend to not counter jungle. The jungle role teaches you a lot about map awareness which is crucial to being good in every lane. An easy jungler would be warric.
Definitely top. You need to learn basic farming skills to be successful in the other roles, and top is essentially just about farming since its so far away from the other lanes. Afterwards it really doesn't matter, but you should know how to play every role so when you need to play a role you didn't plan on playing it wont be an issue. Also, knowing how to play every role greatly helps your interaction with them in order to compliment their purpose and further the team.
As far as a champion goes, I would pick up renekton personally if you can. He has good damage, sustain, and if you can play right is pretty hard to gank effectively, so he will be a good champ to start off with IMO.
in the current meta a lot of top laners dont go ham like riven and darius all the time they play like nasus and sion so now is a good time to learn top because you can learn map awareness (tp to dragon) farming well (you have few fights) and you learn when to engage and stuff since youre usually the initiator. afterawrds i would learn jungle then adc then mid
I think it depends on your playstyle. You could go a few different ways.
One is learn ADC - this will help you get better at support too, because you will see what you would like your support to do in different situations. Also forces you to learn last hitting well - a skill you can use in any other role.
If you like support because you like supporting your team, jungle would be the next best thing. Lots of utility/tank junglers you can try.
Blitz/Thresh/Sona are pretty aggressive supports, so if you like fighting/trading, you could like mid or top as well. And if utility is more your style, utility mids are fine to play.
Personally, I was a support main and drifted into an ADC/Mid player. I can't stand top because it's a totally different playstyle.
jg first something like nidaee or sejuani why jg cause being a suport is all about making plays or not making plays and thats something that comes back in the jungle
as a jungle main i feel akwardly comfertable playing suport
when i first started playing jungle nidalee i had practised suport nidalee allot first sure its a bad pick but it made my jungle nidalee pretty good since as a suport all you be focussed on is hitting those spears
