When i play a blitzcrank to the battlefield can i equip a gear before he pulls a unit

No — you can't squeeze an Equip in between; equip before you play Blitzcrank, or wait until the chain is completely empty.

The moment Blitzcrank resolves and enters the board, "When you play me to a battlefield" goes on the chain as a pending item, and a chain existing means the turn is in a Closed State — only Reaction cards and abilities can be used there (Rule 309.1.a). Equip is an Activated Ability with Main Phase / Open State timing and no Reaction, so it can't be activated with his pull trigger sitting on the chain (Rules 151.2, 381). Practically that means you attach gear first, in the Open State, then play Blitzcrank.

The one exception is a Quick-Draw gear: it has Reaction inherently and can be played and auto-attached at Reaction timing, so you can attach one in response to his trigger (Rule 819.1.c–d).

Also plan for the follow-up: once the chain clears and the pulled enemy unit is standing at Blitzcrank's battlefield, a Combat Showdown starts, and gear activated abilities can't be used during a Showdown — so if you wanted the Might bonus on him for that fight, pre-equipping is the only line.