Tinker is a pusher/counter that can use his abilities to harass and zone the other team out of teamfights and with some decent farm can use his rearm to spam out items like scythe and shivas durring teamfights.
You Want to get your bottle as quickly as you can so you can harass with your rockets in lane and to get some extra regen since you start with only tangos
Boots of Travel are a necessity on tinker with there coupled with your rearm you havc global ganking power and can push every lane with little effort. Soul ring will also give you some more mana to spam your abilities and rearm at level one can be expensive and using soul ring immediately after it completely negates the mana loss Force Staff is gotten so that while you are globaly pushing in sticky situations you can use it hide and quickly tp out to avoid death.
Scythe of vyse is an essential item for any tinkers build this coupled with your rearm can be a perma hex on anyone without a black king bar. Shivas is good on tinker not only because it helps counter push but also because with rearm can produce huge amounts of team fight AoEs. Linkens is often gotten on tinker because it will increase his mana pool and regen and is a defensive item which proc can realy help you escape if you are caught out while pushing(note rearm does not refresh the cooldown on linken spheres passive)
Black King Bar can still be a decent pick up on tinker if the other team is constantly locking you down but an important reason it is not picked up often is because rearm does not reset it's cooldown
One of the biggest benefits of leveling up march of the machines first is the ability to farm the ancients at a low level so if you can durring the laning stage try to have one of your supports stack them for you if you can this can be a great way to to make a comback if you have a bad lane experience
This is my first guide please comment with sugjestions and will probably add more in the future