RE: Need help to build my first team
First off, welcome to the world of competitive play. I'm not as experienced in VGC as others here, but I can give you this fact: weather is everything. You need a weather or a team for anti-weather to succeed, unless you try Goodstuffs, which is somewhat anti-weather on its own. Tyranitar, Politoed and Ninetales are considered the primary weathers, while Abomasnow is the anti-weather, as Hail has no good abusers. It only serves to take away other weathers. Second, I should point out that Infernape is not the best revenge killer, even moreso in VGC. It is more suited to being used alongside Latios/Latias or something similar due to their synergy. But before you even use Infernape, you need to decide your playstyle. Rain, Sun, Sand, Hail, Trick Room, Gimmick, Goodstuffs (cookiecutter utility teams), etc. Do that before deciding on a Pokemon, or you can select one (or two) to base your playstyle off of. Last, Things like hazards and switch moves (U-turn, Volt Switch) are not recommended. Spread moves like Surf, Earthquake and Rock Slide and PROTECT/Detect are standard. The game goes by so fast that stall is pretty much unviable. Speed (or TR) and power are highly regarded in VGC.
A good VGC core for beginners is Rotom-W & Metagross, two bulky tanks that complement each other well and are a very good type and strategy base for teams. They are not easily broken apart. Thundurus-I is big due to its priority Rain Dance, Thunder Wave and Taunt. Terrakion is one of the best physical attackers, obviously, and the same is true for Latios on the special side. Rain and Sand are the most common teams, and Excadrill, Garchomp, Ludicolo and Toxicroak are seen often as a result. Scizor, Gastrodon (general rain counter), Chandelure (TR counter) are great anti-meta Pokemon. Cresselia with Icy Wind is the best mixed wall/support Pokemon most teams can have. Hitmontop and Landorus-T are the premier physical tanks and Intimidaters, but there are not many special tanks (a common one is Gastrodon). Reuniclus can be teched on teams as a counter for TR, which uses Conkeldurr alongside that same Reuniclus. The Discharge-Earthquake combo is often seen between Zapdos, Magnezone, Garchomp, Landorus, Thundurus, Rotom-W and Mamoswine. This seems to work best in weatherless or sand teams.
That's the info I know right off. I would consult the other members of this site on further info, and you can get the full detail from Smogon. Have fun, I did what I could in 10 minutes.
~AoH