What Pokemon are worth unlocking a second charge move for?
Basically, it seems that we have 4 tiers of costs for unlocking a second charge move.
Legendaries: 100k dust / 100 candy
5k buddies: 75k dust / 75 candy
3k buddies: 50k dust / 50 candy
1k buddies and starters: 10k dust / 25 candy
Which Pokemon are worth the investment? I have under 400K dust so I'm not planning to do anything outside of starters for a long time until I know for a fact it will be useful or the costs get reduced.
Legendaries worth considering:
Mewtwo because you can lower the amount you need to power and have multiple useful movesets.
Kyogre with Blizzard for PvP maybe.
Rayquaza to have both dragon and flying offense maybe?
Groudon for both ground and pseudo-grass offense?
75K tier:
Metagross and Tyranitar for PvP coverage?
Blissey for the same?
50k tier:
Rhyperior for ground + rock coverage?
Gengar for Ghost + poison?
Arcanine to get Wild charge for PvP?
10k tier:
All decent starters?
Golem (especially Alolan Golem?)
Answers
Honestly? At the current moment, none. It's never a wise thing to rush into a new feature whenever it comes to Niantic. TSR has already found a handful of bugs and other things.
The stardust and candy costs are absurd. And let's not forget the inconsistency between them as well. Basing the cost of unlocking moves after walking distance just doesn't make any sense to me. It's wishful thinking but if I were you, I'd wait a bit and see if Niantic decides to maybe re-work the cost.
Given how PvP just came out, I don't think you'll miss out of anything by waiting a bit before unlocking a second move. We still need to get a good feel on all the changes. But those are just my thoughts.
When you unlock the second charge move, it randomly selects a charge move from that Mon's movepool (except for the charge move it already knows). If you don't like the move you get, you can use a charge TM to change it. Legacy moves are excluded. In battle, you now have two charge move buttons you can click on, and your quick attack charges both moves simultaneously. As expected, if you have a two-bar move and a one-bar move, the two bar move will charge up faster.