>>42470058What others have said + DO NOT just start breeding to make a team off the bat. Use rentals first and learn the game. Breeding isn't that bad this generation, and making pokemon you want is easier than ever, but it's still a time investment. And even before you start breeding, use your team on Showdown first to see how it works and make adjustments there.
Once you've used rentals and played showdown a bit, decide on what pokemon you liked the best from the rental teams or test showdown teams, and build a team core of about 3 pokemon. This core needs to cover each other's types but most importantly, have a strategy or a plan to win. Then, fill out the team with stuff that counters your counters and covers weaknesses. For example, if you are weak to Trick Room, consider having half your team capable in Trick Room.
And just have fun. Pokemon isn't like LoL where you can make millions playing. Just take it easy.