Battle Spot team building help

[Liberal Army]

Hey y'all,
I recently got back into the competitive scene of Pokémon and I want to increase my rankings on the Battle Spot (Singles).
Since it is a 3v3 (rather than the 6v6 I'm used to) strategies and team building are different than the latter.

I tried building teams myself, but the battles were so close every time and I kept losing to annoying Asians with their stall or Ubers team.
So can someone give me tips for Battle Spot team building, what to do and what not to do, and then help building a team?

The Pokémon I want to put on my team regardless are Kangashkan (Mega) and Gliscor.

 

[skyburial]

Solid choices all around. I'd go with this set for Kangaskhan:

Kangaskhan @ Kangaskhanite
Ability: Scrappy
EVs: 4 HP / 252 Atk / 252 Spe
Jolly Nature
- Fake Out
- Double Edge
- Low Kick
- Sucker Punch

This set lets you OHKO almost anything. It's the standard.jpg build. Scrappy lets you Fake Out ghosts like Gengar to break sashes. Watch out for stuff like Gourgeist and Jellicent that naturally counter this mega. I would reccomend running this as one of its partners:

Aegislash @ Weakness Policy
Ability: Stance Change
EVs: 252 HP / 252 SpA / 4 SpD
Quiet Nature
- King's Shield
- Shadow Ball
- Flash Cannon
- Sacred Sword/Shadow Sneak

Shadow Sneak is particularly useful if someone predicts your switch and activates Weakness Policy, while Sacred Sword lets you hit Bisharp.