Hello Jebus, I'd say that first you would need to make sure you got runes for :
- supporting (like flat yellow/purple armor blue mr and red flat gold or something like that and not the random **** i see all day on supports)
- ad (like flat ad red/purple and armor yellow, mr blue)
- and stuff for top lane/mid depending on the matchup
- stuff for jungling depending on your jungler/you strategy (counter, camper etc.)
Whatever you probably know that already.
First Blitz, he can be played jungle and support obviously, I think it's a great SNOWBALL support. I insist on snowball. That is to say, not good on soloQ if you don't know who will lane with you (maybe a total idiot unable to follow your engages for instance). However in duoQ, against some no escape ad especially, you can crush lane and snowball really hard (I'm more thinking about leveling snowball and not itemizing snowball :p).
*Banned on ranked? Not really from my experience, well it happens but Sona is like much more threatening (anyway there aren't much support bans like in competitive play). I see no reason to pick Blitz else than "I want to play my weak ad and once I've been traumatised by a Blitz; plus I have not enough micro to avoid hooks"
Jayce, is the hero I'd recommend to you. It's not the easiest hero to learn (you got potentially 7 spells, and cooldowns that you need to manage). But once you got the trick, it's really not hard to play him correctly.
He's a SAFE pick in soloQ, you can firstpick him, it doesn't matter because he got no true counter.
There is only safe counter picks like Nidalee, let's say Yorick. Even if, once you got your Bloodthirster, Yorick can't do much against you anymore.
Tbh, the most solid pick in soloQ is Jayce for now. However it's a Pick or Ban so...
Rumble is strong, really strong but he's situationnal. So yes, if you got a easy melee top lane (I don't know, let's say Wu kong) or a weak early enemy (like malph, or a bad Udyr) you can crush him so hard that he will either : - leave lane / -leave game.
But you will need a good jungler (that gives you some cover, because you'll probably be pushing more than your opponent), and a perfect warding.
Let's make it easier to picture. Imagine you're bot side, you got to lane top against Irelia. There is Lee sin as jungler against you. Well son, you better hide inside this bush, because if I'm this Lee Sin, you'll probably lose at least a Flash and be forced to go fountain because I'll camp you hard. And once you're behind an Irelia with Rumble you better cry at your jungler to come :p
Else, snowballs like no one else, but it is a COUNTERPICK that need a safe lane and to take kills.
So all things considered, I'd tell you Jayce because he got the most competitive value, if you get good at playing Jayce, you'll be able to greatly profit from it. However Rumble and Blitz are funny to play with, Rumble is easy, but with Blitz you'll laugh so hard at your hooks at start and this is priceless.
* Looking for someone to duoQ with me. Got 1400-1500 elo right now, top 1700. I played and won some ESL weekly tourney with my friends, I also play sometimes with my friend's accounts (all at 2k) to prevent the decay so I got some experience (been playing DotA also alot competitively ). Obviously someone within the 1400-1500 radius, I swear if you got the level we bring it on to 1700 and above easily. Can play any role.
* DFG on Vlad is great, it's been a long time that I use it. It's the only way to win some match up, for instance against a decent Jax.