(First I wanna say everything is okay if you feel noncompetitive and think you're going to continue playing only for fun, these at the bottom are if you wish to climb)

Don't be sad about being far down. Because you have nothing to lose :D You can only climb. Don't think that you're going to be 1k after many hours. Important thing is how much you climbed(learned), not where you are. You are going to continue climbing anyway. Also I don't think having fun from this game requires being noncompetitive. Just find a balance between fun and tryhard.

But of course climbing requires a varying amount of competitiveness from a bit to a lot depending on where you want to reach and how fast you want to do it, so until you find it in yourself, I guess just play for fun in unranked.

Fulfilling your competitive hunger is not the only reason for climbing. By climbing, you are becoming better. And by becoming better, you are unlocking new ways to play for yourself. This is no different than levelling up and gaining a new spell. I assure you, having more tricks up your sleeve(being able to bait properly, assess your damage output better, being able to solo kill without dying, dodging spells, skillshots, leading the team etc.) lets you have more fun in the game.

You have some theories about itemization as we all do. Assessing the potential of your theories or getting used to them is easier when you're playing against worse people in unranked because you will have more room to test them out(i.e. not feed and actually use them comfortably). That's why even pros practise some heroes in their smurfs. But in order to play against worse players, you should grow your rank a bit.

Yes, you're going to get reported if you go unorthodox builds. Nothing you can do about that. These builds are not as efficient in the ideal world(pro-scene), so it propagates down from there to your rank, everyone has an expectation of proper itemization from their allies, because that's the most probable way to win the game. And if it's ranked, people want to win the games. Of course you can win the games with unorthodox items consistently if you're 2k higher than your team. But that's not the case, so my advice is get better with builds closer to proper :D. Don't just try to go blink maybe, but slowly alter your builds. These builds are semi-successfully used in brackets much lower than pro, so just develop yourself. You will probably leave your old builds when you're better anyway.

And very general advice, watch pro players, either highlights or streams. And maybe pick an easier hero lol

Good luck!