If you could pick any 10 Lucky Pokemon to start with, what would they be?

Don’t think you can go wrong with some dragon counters... Ray-Ray is overdo, pretty good chance of seeing shiny Latios and Lataias this summer origin form Gritina, Garchomp hopefully becomes a tier 4 staple.... Some Psychic counters are also a good idea we all have 3 months of the lake Trio to get through

For long term I would say Shadowball mewtwo or raikou, but for short term/ kind of low investment, here are my thoughts.

I would say MM Metagross, it might be hard to get candy but trading a high level would be beneficial, for future raids and gym clears.

If they don't have dragonite that might be useful, especially for palkia, also dratini is in raids at the moment.

Rhyperior might be good, but I'm assuming that your parents have groudons, but still useful as a rock attacker. Also Golem, if you really want easy candy 1k walks, and decent rock attacker. Maybe have them go ground if your parents don't have enough machamps other fighters/ground types for dialga.

If your parents are interested in gym defending, then a lucky chansey/blissey would help alot.

I have a lucky exeggutor and it works great as a grass attacker(not the highest grass dps, but decent), and also can be a niche gym defender, especially after or before gyarados since it resists both Gary's weaknesses.

It might also be good to consider a swinub/piloswine to prepare for the community day.

Well, I'll first answer to your scenario (rather than the question in the title).

- 2 Machamp
- 2 Tyranitar, 1 with B/Cr and 1 with S/SE
- 1 Mewtwo (With Psychic)
- 2 Dragonite
- 1 Metagross (MM)
- 1 Kyogre (assuming you have extras since they came back before it left. However if your parents have Kyogre themselves you can consider dropping it for an extra machamp or tyranitar (B/Cr))
- 1 flex of Rhyperior / Feraligatr / Exeggutor depending on preference/local spawns.

Basically the Mewtwo will help them a lot with Machamp raids and won't otherwise be attainable. Mewtwo and Kyogre are the two legendaries the most "better" than the next best of type in my opinion (Rhyperior is close to Groudon, and Dragonite is close enough to Rayquaza). I wouldn't recommend too many legendaries as it's costly to you to give up for the trade AND they probably don't raid a tonne so they won't have loads of rare candy to use to power them up.

Dragonites I assume you'd have plenty of extra from the community days. They're also useful immediately for Palkia, so your parents can see the value quickly.

2 Machamps to give them a head start on preparing for Dialga raids and in general to max out. They can get the other 4 themselves from raids.

Tyranitar likewise is good for raids (both B/C and S/SE). Having a base of 2 to start with and getting more from raids is good. Basically, you give them a base to see how strong they are to motivate them to raid for more.

Metagross is finally a great generalist with a legacy move your parents can't otherwise get.

The flex comes down to preference. Rhyperior is just a much cheaper version of Groudon for them. Feraligatr likewise to Kyogre, and water is a useful type a lot of the time so perhaps they need more than just the Kyogre. Exeggutor can be versatile and will further help with Machamp raids. There may be other good picks or it may come down to what you're willing to part with though. (Also don't trade stuff that's overleveled, colossal waste of stardust!)

Now, to answer the title: if I could pick any 10 assuming I had a blank account:
- 2 Rayquaza
- 2 Kyogre
- Raikou
- Mewtwo (SB)
- MM Metagross
- SA Moltres
- Groudon
- Shadow Claw or Lick Gengar

Basically there's no point in Machamp or Tyranitar on your guaranteed ones because you should get enough of them to continuously trade and get lucky ones eventually naturally. Stick with legendaries and legacy pokemon that will be useful.

If I'm adjusting for what I have (two maxed SB Mewtwo, two maxed Kyogre, two maxed MM Metagross and 4 more at 35+, already have a lucky Groudon, maxed SC Gengar): would probably drop the ones listed in the brackets here and replace those 6 with a dragon HP Togekiss, a level 35 Swinub/Piloswine, then probably one or two each of Rampardos and Garchomp (or their first forms) when they become available.

Contrariwise, I'd recommend starting with pokemon that are not currently readily available as raid bosses. Sure the savings for stardust is nice, but in the long run not as important.

Machamp's best moveset is still available, so you can trade dozens of high level Machops later to try for good IVs. The guaranteed lucky are best used for something that will be harder to grind later.

Metagross with Meteor Mash
Kyogre with Hydro Pump
Raikou with Wild Charge
Tyranitar with Smack Down
Dragonite, Latios, or Rayquaza with a dragon/dragon moveset
Mewtwo with Shadow Ball, if you have extra. (If you are feeling really generous, with the second move already unlocked)

Maybe:
Venusaur with Frenzy Plant
Charizard with Blast Burn
Moltres with Sky Attack

However i'd actually recommend saving some luckies. A lot of CD moves are fantastic, and getting guarenteed good iv/half stardust cost versions of them will be fantastic. When gible is released, you can get guaranteed ones, and gible is going to be an absolute beast, though depending on how your dragons are looking (such as i you have a large number of them), i'd suggest not evolving until we get a community day in the future. Same applied for Bagon, whos likely to get a community day.

Currently released pokemon i recommend, Meteor mash metagross, its one of the best attackers in the game. One or two will be enough, for as good as it is, it doesnt get many specialist-steel match ups, so only 1 or 2 will be more than sufficient. Other than that, i recommend saving your remaining luckies for future pokemon, the top tier community day ones, and likely future CD ones (bagon and gible)

However if you arent the kind of person who wants the absolute most top level pokemon/short man raids, i'd recommend getting luckies of pokemon you like if that is more your play style.

You might consider trying to arrange so that both of them and you get a lucky Rhyhorn/Rhydon. There is a realistic possibility that Rhyhorn will get a community day, and that the evolved Rhyperiors will get Rock Wrecker as a move. Want to be ready for that, so get the lucky Rhyhorn/Rhydon, and DON'T evolve it to Rhyperior yet.

Dark Tyranitar is easily obtainable from raids, but Rock Tyranitar is not and is thus a good candidate. Other elite legacy mons that have already been mentioned include Mewtwo (with Shadow Ball), Gengar (with Shadow Claw or Lick) and of course, Metagross (with Meteor Mash).