The average player believes that Tinker is strong earlygame but becomes weak later on. Though nothing could be more false than the second part of the statement, the average player is right in thinking that Tinker is strong earlygame. Our main spell at this point is Laser, which is very strong. Once you hit level 3, Laser is strong enough to do serious damage, but you should still use it somewhat sparingly unless laned against a low hp hero. At level 5, it will generally be worth using Laser every time the cooldown ends. Our goal is to outfarm and outlevel our opponents, which we achieve by harassing and hopefully forcing retreats with Laser. Good chicken use helps in this regard by allowing us to never leave the lane. Note that once Missile hits two targets, it does do more damage per mana point if against two heroes; if laned against two low hp heroes, you may consider spamming level 3 and 4 Missile instead of Laser, although in most circumstances the higher focused damage of Laser will be more helpful. At this stage, we do not expect kills without allied help- our goal is to build up advantage over our opponents while working towards Boots of Travel. You may be able to get a sneaky kill by hiding behind trees, then ambushing and casting Laser and Missile on a clueless enemy hero, but don't count on it. On the other hand, if we have an allied nuker in the lane, consider being very aggressive to get kills- Tinker with another nuker can kill many heroes from full health!
After getting some basic items and Boots of Speed, it's time for perhaps the most difficult part of the build: saving 2200 gold to buy the Boots of Travel recipe. At this point, I strongly recommend buying a set of Observer Wards. I cannot stress enough how helpful Observer Wards are. Apart from the standard significant benefits of avoiding ganks (one gank avoided is worth about two or three sets of Observer Wards), Observer Wards help Tinker in particular because the extended vision