Help Me Not Suck (Please)

I used to play a lot of league back in... Oh, I dunno, 2012? Lost my laptop to some bad times and fell out of it. I finally have a shiny new gaming laptop, and decided to jump back into the chaos. I remember being average at best; not necessarily throwing my prone form into the enemy's hands at the first sign of combat while also not necessarily destroying all champions that dare grace my presence. Friends here and there have continued to play or follow big teams, and as a conversation survival strategy my brain has remembered most of the basics, and I picked everything back up pretty fast when babying myself in training mode. Got my ass handed to me real good when I tried playing with the big kids, so I stuck to the bots instead. I moved onto Co-Op VS A.I on intro, and after a bit of a learning curve got into a pretty decent groove. Now... The problem.

For some ungodly reason, I am competent until put into Beginner mode, where I am suddenly godawful at everything I touch. Seriously. I've sworn off trying to play with real people for now, and am only doing Co-Op vs A.I. till I get my sh-t straightened out, but even that I suck at somehow. I can handle Intro mode no problem, but every time I get comfortable playing a champion and try to go into Beginner, I am suddenly competing against myself for the title of World's Best Feeder. I've been trying to read up, and feel like I understand the basics, I'm just not sure where I'm going wrong.

The champions I've gotten accustomed to playing are Veigar, Garen, and Panthion. Usually I call top lane, and on Intro I can hold my own up there and push through with relative ease, minimal death, and a decent kill count. It's when I try to move out of Intro that I seem to be catching a snag somewhere. I've noticed the bots put on top in Beginner are almost always heavy hitters (guy with an ice club that deals what I can only describe as 10d12 emotional pain straight to the heart and another I'm not sure how to describe) that simply do not agree with just one close-ranged fighter with no healer (Garen and Panthion), and on bottom lane it's ranged attackers I struggle to survive long enough against to even consider hitting back. I know this now, but don't know what to do with that information. I've tried everything from waiting them out and striking when it's opportune for me then sprinting back to the sweet, sweet safety of the turret I'm barely protecting (which usually means I spend the whole game holding off minions which is boring), to running in full-force and doing as much damage as possible without dying, repeat but WITH dying, and a mix of all three.

I hug my turrets when needed, I run and avoid when I realize my attacks aren't doing jack, and I try to follow suggested builds for my chosen champions to a T (now that I know they exist). I know I haven't been back in the swing of LoL for long, but I feel like I'm doing something somewhere horribly wrong to be failing so consistently at something so seemingly simple. Any advice? I honestly don't understand what I need to be doing to get better, and at this point I'm worried I'll be stuck on the intro setting forever. Feel free to read me to filth, I could honestly use the guidance lol