Buy Magic pen marks.
Get another rune page for support if possible
Buy everyone up to 4800 ip and play them. (You will understand how they work, combos, counters, strong and weak points.) additionally, you can pick for other people.
Consider looking up high elo players and copying their masteries.
Generally you want to stop at 21 in one tree.
Don't take perseverance. Veterans scars is nice.
Take improved flash when you put any points into Utility.
Scout is considered useless. Don't get strength of spirit. But in that case, you would never go 30 into support.
Alrighty, I'll keep going.
Riven mastery page, she scales off of CDR and AD
Don't get the attack speed. Cdr will help her more.
No clue what mastery page 8 is for.
Mastery page 7, take veteran scars in defense.
For AP consider grabbing improved flash and Cd on summoner spells.
Spell sword not work in on most AP mids. They don't autoattack often. Especially lategame, where spellsword is designed to shine.
Try not to take butcher unless you have nowhere else to put the points. Practice CS'ing. 100 creeps by 10 minutes is perfect. 70-80 is considered really good.
Irelia, grab 21 into defense, because she's designed to dive carries. In oder to stay alive, you want the bonuses for building defense. Grab the improved ignite mastery, 3 in CDR, and get Armor pen in offense.
If you have any more questions, you should ask around.
These things are easy to fix and work on. They improve your early game by alot.