Max Laser and Missile for better nuke and more successful gank(s).
Rearm doesn't really have to be in level 9. Take it earlier if you got BoT faster. Nonetheless, take Rearm in level 9.
You may skip the level 10 Talent because it doesn't change much. But if physical carries bother you, take the armor instead of the int.
I personally max all Tinker's skills before taking level 2 Rearm, and the reason behind this is because of the low-mana cost of Level 1 Rearm. But if you need more speed, don't bother taking Level 2 Rearm.
I postpone taking Level 3 Rearm because of its high-mana cost (300 mana cost) and low mana pool of tinker makes him do less than expected. I only take Level 3 Rearm when I already have Scythe and/or BloodStone. Why? Because Scythe needs faster Rearm cast time to work well. Even a split-second might make the enemy use BKB or stun or something to escape. There are some games that even if I'm level 25, I still have level 2 Rearm. I'm not sure but maybe gaining XP has been easier this 7.00 patch.
You buy Null Talisman for cheap stats + damage, to get those farms without getting denied that much. Prioritize getting the ranged lane creeps and the large tower-attacking creep. Use laser to get it if necessary (Laser is true damage, so it will deal 100% damage on that large tower-attacking creep). You can also blind the enemy, then get the creep uncontested (deny).
My style is, harassing the enemies with attack + laser + attack then repeat after Laser CD until enemy's HP is low enough to die from Attack + Missile + Laser.
Sometimes, if I am dominating the lane too much and I don't need sustain that much, I rush BoT (Boots of Travel), skipping Bottle. But if I need sustain, I buy Bottle first, then buying BoT next. I buy Soul Ring after BoT. Then Dagger next, for the Rocket > Dagger > Laser combo.
ALWAYS USE SOUL RING BEFORE YOU USE SKILL OR REARM (Except if you're in the verge of dying).
Nonetheless, use Soul Ring before you skill to have enough mana for your skills.
What I do in farming using march is, March > Soul Ring > Bottle > Rearm > Soul Ring > March > Bottle > TP to base. Well, if I already have my Dagger, I'll use Dagger before the first march and before the TP to base. Well, the arrangement of March + Soul Ring + Bottle isn't necessary, as long as you use them before using rearm, you're good to go.
Null Talisman >
Soul Ring >
Aether Lens >
Dagon 5 > (My average time having all items up to here is 25-30 minutes)
(If I'm getting many kills) = BloodStone >
Sell Bottle or Store it on Stash/Backpack >
Another Soul Ring >
Scythe Of Vyse (Switch between Scythe and Soul Ring when going for kills and when farming)>
Ethereal Blade (Let the Aether Lens stay on your backpack/stash) >
Equip these items for: FARMING/PUSHING
Shiva's Guard + Soul Ring + Aether Lens + Dagger + BloodStone + BoT
Equip these items for: KILLING/TEAMFIGHT
Ethereal Blade / Aghanim's Scepter + Scythe of Vyse / Shiva's Guard + Dagon / Aether Lens + Dagger + BloodStone + BoT
A Tinker player should position himself nicely and properly. Don't go in the middle of fights and end up being able to do nothing. Always stay at the back of your team, (except if you're confident enough that enemies won't be able to react when you go in XD).
Use Agha + Shiva's IF: Enemies have many units (Ex. Meepo, Phantom Lancer, Chaos Knight)
Use Ethereal + Scythe IF: There's a single hyper-carry in the enemy team that needs to be nuked(You know, one-man army like the OverPowered Monkey King)
Use Aether Lens IF: Enemies have too many stuns [better positioning through Aether Lens(Longer Cast Range)]
(Using the Nuke-type build) Missile > Dagger > Scythe + Ethereal > Dagon after Ethereal hits + Laser > Rearm (and repeat)
(Using the Army-depleter build) Shiva's Guard + Missile + Laser on creep near you and enemy hero > Rearm (and repeat)
I hope you learned something new in my guide. Any questions, clarifications, and/or suggestions? Comment and if I have time, I'd read them. Have fun playing in 7.00 patch! :D Good luck and do your best :)