Play Heroes who can Snowball Effectively thru early- mid game. Good Examples are PEbbles, Dw, Devourer,Fayde. Instanly Call Solo mid, then pick one of there heroes( I prefer pebbles, hes OP at the brackets u play) and "farm" or lasthit 6-8 minutes in mid. If ur Team doesnt get u rune ward, buy it urself, u could afford that before or atleast 6 minute mark. Now once u are mid u need to do some observation. Can u gank, Which lane u should gank, when to gank, and what is good rune for gankin. Also, dont forget to call misses, theyre extremely important and if some of ur sidelanes dies becouse of that u didnt call misses, its 80% change they Q.Q to u and say u fail middle and ur trash and terrible.
Some of the runes which are extremely good for gankin' : Invisibility,Double Damage,Haste. If u get some of these runes and u can gank(Look if ur sidelanes arent pushed to the enemy towers so u can gank safely) Go for it and grab some kills, or assists. Rune control is rly important. Never gank if u arent 100% sure u have enough mana. GO back first and then Tp, so that enemy cant see u and dont know what to expect.
Thats all i got for now. Im scrub too(almost 1500) but i know alot more than normal 1500 would know, just becouse i watch alot of AngryTestie and Moon and Shamsz and all those popular streamers. ALWAYS Watch Streams/Or stream replays, theyre very usefull for u for little tips and tricks. U dont need to be as perfect as them and "Do tha maff" just few tips and tricks are usefull and improve ur gameplay very much.(If ure not familiar heroes i listed, go play them on public games and practice mode.