So about TvT.
We can all safely say the Gasless expand is a dead build. Sure it is possible to get away with it but very, very risky to perform. Since that is what I always did in WoL I came up with a build that I started doing after the free siege mode was introduced in the beta.
10 Depot
12 Rax
13 Scout
14 Gas
15 OC
15 Marine
*If I scout that the opponent is probably going Reaper the build changes just a very touch. If I see Reaper I get a second marine out.
Reactor Rax -> Constant marine
Factory -> Tech -> Tank
Port
Push @ first tank
Rally all structure to opponent natural
You will float a bit of cash after putting down your factory so try and overmake some depots. You really need to constantly be making those even if you don't "need" them at one point in time. 2 food from your rax, 3 from your fact and 2 from your port eats up supply fast. There will also be times you need to cut SCV production for a few seconds to renew your marine cycles. I don't have the timings for those down but you can fairly easily see if you can afford it or not. The main goal is to always be producing attacking units since you need your initial push to succeed or you'll probably be very far behind. When you first push out it will conflict with your depot timing (generally depots win out over marine production) but you want your marines to win out this time. You really want those extra two. Every last man counts on the first push. So you'll take a minor supply block so stop SCV production for a bit to free up supply.
You will have enough money to add a second tank. Do that before using the Starport. Once you have the money make a Viking and don't stop making those until you get 3. Once you get 3 consider adding a reactor unless he has also started Viking production. If so keep making Vikings.
Basically you just tank contain from this point. The entire goal is to secure your natural before he secures his natural. Often times they'll have siege available but you will have the overwhelming numbers and vikings to control the space. If you can break the ramp then break it. If he has 2+ tanks don't attempt. Just set up a hard contain. Get your marines in bunkers (generally behind your tanks so his tanks can't get free shots on them) and consider a turret.
The big heel of this build is if the opponent went fast cloak banshee. Generally the best idea for this is to abandon his natural and immediately throw down an ebay. He won't have the forces to hold his natural so with your scout SCV (who is probably just hanging out at a tower) build a turret at his natural secured by your forces. At this point you can't really threaten his main but you can still turret/bunker his natural while you double expand. Tech your port and get a Raven out then switch your Rax with Port to make up 4 more vikings as your anti-banshee force to keep your main safe while getting stim out and making another rax to get a reactor for marine production.
That is what I do because I'm a marine/tank TvT player. But honestly you have no investment in bio if you prefer to go the mech route. You can also cut out tank production if you wish to go into pure bio.