Another thread mentioned this site, which I feel is worth repeating:
http://lolecho.com/?na:1733897352
Some bad news: if you're just hitting 30, you will probably wind up in low Bronze. The initial placement matches tend to be around Silver IV, so you will lose more than you win until you reach your skill level. It's not a bad thing, just a reality you need to prepare for.
If you want to improve, here are some good specific starting points:
- Finish at least a couple Rune pages with logical Tier 3 runes. Any guide or a site like probuilds.net can help you out
- You need to last hit better, even if that means picking a champ better suited to it, like Zerath or Ziggs.
Just 1 & 2 together means, by 10 minutes in, you're some 1200g behind your lane opponent. It's very hard to come back from that.
As others said, wards will save your life. You get a free ward trinket, but you don't use even that.