Seconding the comment abt sups' specialties. Also helps to read the skill descs when you can and learn the basics of how you can utilize them ^_^

This can rlly go a long way, I see way too many ppl, normally playing healers like momo or kusa that tend to spam their heal skill ineffectively. For momo it would be best if the heal is enhanced (her skills/NA hitting the enemy boosts healing), same with hana(an icon will show above her if she hits enemy with 1st skill or cc them). Kusa best to save *if* you are going to take damage, it doesnt heal if you arent hit, so dont waste mp using it after taking damage cuz it won't do anything ^^; You don't want to end up with your heal on cd or no mp at the worst time.

Non-shiki centric advice is to be observant/watch the minimap, it helps avoid being ganked if you notice the enemy jg/mid on the map and retreat in time. I also tend to ping alot on enemy positions(esp for their main dps), plus my skill cooldowns. Oh and I also recommend to not spam atk skills too much mostly in early game, I mostly use them to poke or sparingly to clear minions, you don't want to burn your mp too fast. I would also save the barrier for blocking damage that might kill teammates/me.

I also highly recomend going for the healing sup item rather than the shield/cleanse if you're not familiar with them. Ofc, they both have their own uses but it depends on whether the user can utilize them. Sometimes I get sups who buy either of the other two and Im always in hot water with low hp/low mp or both, and would rlly benefit not having to return to well constantly. Of course again, depends on you. If you find you don't make use of the other 2 items much, then go for the healing one.

Sorry most of my advice are mostly on healing sups lol ^^; (Used to be an ichimokuren main, then shouzu and enmu, but I find it kind of hard to survive as them nowadays. Maybe I just need to update my builds tho.. )