So I'm still a relatively new LoL player (Only hit lvl 30 a little over a month ago) and while my goal has always been to eventually get into ranked, I told myself "at least get 200 normal wins so you get used to the game more". Well that time is fast approaching and I feel even more unprepared to go into ranked that I did when I started.
Then don't go into Ranked. If you don't want to play ranked, don't.
The problem arises if and when I end up in my secondary role. There's always kindly asking, but if normal are any indication, people aren't too happy to swap it up (unless i tell them their bot is duo'd que'd, but that won't help since I'll probably be doing solo que in ranked for at least the start).
People don't like swapping lanes in champion select, and if you can't play at least two roles reasonably well, you aren't ready for ranked. I would recommend learning a second role before going into ranked.
Lucky for me I have a friend who's been incredibly patient with me and has helped me learn a lot about the game and the role I ended up in (adc). While I feel pretty confidant about going into ranked as an ADC (I'm not perfect, but I have to start at some point). Said friend is now pressuring me into going into ranked and at least getting my placements so we can see where I end up.
As you are now, I guarantee you will end up in Bronze. I can play all the lanes with some degree of competency and I've still never broken low to mid Silver - and even then I'm not sure I deserved it; it was a win streak during placements when I started Ranked back in late S4.
So that's where you are. Let's look at where you want to be:
I've been putting top as my secondary, but i can't seem to handle melee characters mechanics. Not sure why, but nothing clicks for me, and I really seem to struggle with initiating engages or getting to the right targets in team fights without being kited. "Go vayne/quinn top" would be a temp fix, but I wouldn't feel comfortable doing that if we don't have a tanky jngl and sup. (Been playing 
in top. Only success I have is split pushing as nasus and running around like a jerk as garen)
For top, since Garen is where you've had the most success, I would focus on him. Initiating fights can be kind of difficult with some champions. You generally want to start with a high-impact ability (Strong initiatiors include champions like Leona, Vi, or Zac due to their ability to close distance and apply CC at the same time). For Garen, you pick a target and hit them with Q->E, using your R to execute and your W to not die. Not getting kited is hard though, as kiting is Garen's primary weakness. I would recommend trying out some tanks like Maokai, Cho'gath, or Malphite if you want to practice starting teamfights.
I'm wondering if mid may be better? I've been told many times to not try it as a new player because it's a lot more "meta" and that I need to play way better than bot or top. Is this true at all? I find ranged and being squishier a lot more comfortable which mid gives me (most of the time). Do I need to learn more meta/macro things before attempting to learn mid? I've played some azir games and he's pretty fun, but I'm far from good at him (can push lane and poke, but never secure a kill).
First, whoever told you not to play mid is stupid. Mid is the second easiest role for an ADC main to transition into. On a larger scale, your role is the same - damage, usually at long range. Midlaners, however, are mages and assassins instead of marksmen, so you are typically doing most of your damage in one burst. For an ADC main, I would recommend Azir (although he can be difficult to play), Varus or Ezreal (ADCs that can be built as AD midlaners), or maybe Annie (How to Play Burst Mages 101). I don't have any personal experience with Azir, so I can't really help you with your gameplay there.
Jngl has way too much macro play for me to pay attention too (I've done it before and it's been pretty embarrassing how bad my ganks can be).
It is true that jungling can be difficult. Frankly, I would consider it the hardest role. However, it isn't impossible to learn. For an easier "intro to jungling" champion, I would pick Warwick or Nunu, for ganking and farming respectively. Once you improve, I would look at Shyvana (simple but strong - run up to them, hit them with your E, and auto them to death), Volibear (if you have success with Garen), or Kindred (the marksman jungler, since you like playing ADC). For ganks, the trick is to learn when it is actually possible to gank and then only gank when those conditions are met. For example, if the enemy laner is close to their turret, a gank will most likely be doomed to failure. If your laner is too far away from the enemy or has too little health to follow up, it is also very hard to gank. Dragon control isn't that hard - just ask yourself this: 1. Can I solo it, or do I have adequate help? 2. Can the enemy team reasonably contest it? 3. Are there enough wards for us to see the other team coming and get ready if they want to contest? If the answers to those questions are yes and no; or yes, yes, and yes; it's a good time to take dragon.
I would go support, but I'd end up a support main if that was my secondary.
Regardless, it's a useful role to learn and I would consider it the easiest one for an ADC main to get into. You spend most of your time laning with a support, and now you are the support. Good "starter" supports include Leona, Soraka, Nami and Sona.
