Masteries are 0/18/12 with Windspeaker's Blessing at his keystone, (odd duck for a tank support). Courage of the Colossus isn't particularly great once you're out of lane because you won't be engaging all that much and Taric's CC isn't reliable enough for Stoneborn Pact, which is fine because you have your own healing baked into the kit. Again, odd duck.
Skill order is E-W-Q to start.
Then you can either max E or Q first, both are perfectly viable. Generally speaking, max E vs. engage supports (Thresh, Blitz, Leona) and utility supports (Janna, Nami) and max E against poke supports (Zyra, Brand). These aren't hard rules though. You have until level 4 to commit to any skill ordering. This is particularly important against champions that are combo utility and poke (Karma, Lulu, Sona). As you play Taric you'll start to develop your own style, learn support match-ups, ADC pairings, etc. and that'll influence your skill ordering.
The second skill to max is also up in the air. If you max'ed E first, then Q is next to protect your ADC if they're doing super well. If you have a fed bruiser/tank on the team, the consider going W second because it scales on the target's max health. If you max'ed Q first, then max W next for more raw protection or E for more CC/catch potential and a touch more damage.
For item builds, again Taric is flexible. Default is Relic Shield to start, but in poke lanes (or rather lanes you expect you'll be max'ing Q first and using it frequently) Ancient Coin is viable as well. Also consider your team's composition. If you happen to have several champions on your team that have trouble getting engaging, then Talisman of Ascension can be the tie-breaker in your starting itemization.
For the initial build, it's the usual boots/sightstone/upgrade your starting item in the order you see fit. Boot choices are Lucidity Boots (best if winning), Ninja Tabis (most general option). Mobis (if you plan on roaming a lot), and Merc Treads (buy if the enemy team has a lot of CC, don't just buy for the MR)
If you started Relic Shield, then Eye of the Equinox is a possible item pickup if your team is winning early on and you want to close-out. Outside of Relic Shield, Eye of the Equinox, and Talisman, Taric's core items consist of:
Redemption (most flexible option)
Knight's Vow (build for armor and to protect a fed ADC)
Locket (build vs. magic damage heavy teams or if an opposing AP champ is fed)
Build in the order you see fit, and only build if it makes sense. Locket vs. all AD comps isn't going to help at all. Other items that are fantastic on Taric:
Zeke's Convergence (get your fed ADC absolutely popping and well protected)
Ardent Censer (build if you have multiple AA heavy champions doing well. Taric proc's the passive ridiculously well, possibly as well or even more so than Sona)
Righteous Glory (when you are absolutely the only engage option for your team)
Abyssal Mask (2nd best MR item for Taric after locket, particularly if your team is magic damage heavy)
and for a laugh:
Iceborn Gauntlet (this with Q spam is just hilarious when you're ahead, but only do it to add salt to the wound!)
