1. Do all tutorial quests before starting any real match.
2. Check all stats in wiki site like : Dota 2 Wiki
3. Always practice in co-bot games before using any Hero in pub match.
4. Watch games to learn more about Heroes you wants to play .It is possible to filter matches with hero you looking for.
5. Never use random hero feature in pub match (this for both new and old players).
To play as a initiator / ganker/ support BH, your item build should have
Vlad only if you have at least 2 melee allies
Heaven's halberd if enemy have hard right clickers like void, sniper, troll
And if you are having good amount of bounties then abyssal blade is nice
Apart from these I usually go for
BKB instead of linkin
Deso, MKB, BF to power up the jinada