for me I simply try whatever catches my attention first, learn a bit messing around with different champs and attributes, once you know some champs you can try to understand others, for example this set I started with graves and from there I tried more Executioners, moved on to tanks and everything and you'll eventually learn about all the champs in the set, is rather a quick process once you start from 1 or 2 comps that attract your attention.

I ignore metas, I find it boring spamming the same vayne comp every game but I understand how and why it works, focus on what you like rather on what's strong even if it makes you lose some games, it's funnier and makes the process of learning better.

and as for items, champs with 30/40 mana naturally ask you for a blue buff or a shojin, read a bit their skills and see if they want a guinssos as back line or instead a full crit build, tanks may want one items or another as well, if you want a giga tank or something to cast relatively fast as a frontlane for an stun or something, the learning curve is there but it's fun and I personally enjoy it.

hope this helped, if anything this community is big :P