>>40190523IVs will never change on the mon you invest in, but you can eventually catch/trade into better IVs to invest in until you roll 15/15/15 like your Sneasel.
Generally you don't touch the power up button until you get something important that also has very high stats, like 1 or 2 points off of perfect in defense or health at most.
I've maxed out three Weavile and don't regret any of them, but it's also one of my favorite Pokemon and I've used them over the past year to lowman plenty of psychic/ghost/dragon raids. You'll get the same mileage or better out of Tyranitar for dark dps and Mamoswine for ice dps, but I like Weavile because if you dump the 50K for the second charged move or throw excess Charge TMs at it you get to share the bigger investment of 150-200K dust between two types of DPS as necessary.
>>40190857>why december?Each month has a Community Day event where Niantic makes a special attack available for a specific Pokemon, alongside introducing its shiny and boosting spawn rates. This month is Trapinch. Last December they had a rerun event where all of 2018's Community Day Pokemon had their exclusive attacks made available, along with all the benefits of boosted spawns/shiny rates.
Wait for December so your Charizard learns Blast Burn, which is the only reason you would want to use it.
Your Weavile should be enough to clear gyms with, it's a good attacker to learn how to dodge efficiently with anyway.
Defenders are whatever shitmon you have laying around that you want to throw excess berries at for candy. (rare shitmon you're saving candy for)
