Who and What are the Big Threats in the Current Doubles Meta?

Hi, so I'm not too experienced with competitive pokemon (mostly due to laziness), but I'm pushing past that more lately. I want to build a team, but I'm not sure what to be wary of. Who are the biggest threats, what tactics will be most common, how do I deal with them? These kinds of questions I need some answers for so I can brace myself and build a suitable team. I'm fine with actually building a team as long as I know what I'll be up against.

The only threats I'm currently aware of (from seeing them so much on Showdown since I don't battle on 3DS due to procrastination) are Celesteela and its bulk and power, Toxapex with its hazards and recovery, and I believe also Alolan Marowak with something to counter basically every type. I know against Celesteela, a Fire-type would be nice and a pokemon with Magic Coat or Magic Bounce to mess with Toxapex and a strong Dark, Ghost, Rock, or Ground move for Marowak. But, yeah, as you can see, I really need a bit more info. Any little bit is much appreciated! And apologies if I'm doing this wrong.

Edit: Dunno where exactly to put this, but I forgot to clarify that I meant Battle Spot Doubles.