Raids - Get more Mewtwos or Not?

Yes, get a Tyranitar. Maybe catch some eevees and pinap them, too.

While the infographic could use some updating, the attackers tier list highlights the strongest Pokemon to use on offense, i.e. for raids and attacking gyms: https://pokemongo.gamepress.gg/attackers-tier-list

If you want to hold gyms to accumulate coins for storage upgrades taking a look at the defender tier list would be helpful too: https://pokemongo.gamepress.gg/gym-defenders-tier-list Admittedly the importance of defense depends on your area. If gyms turn over all the time pay more attention to it. If not then you can throw just about anything in a gym and you'll get some amount of coin from it.

If you can get a Shadow Ball Mewtwo from someone I'd do that. It's a top counter against itself and will see massive use whenever Gen 4 drops. As far as other attackers go Tyranitar is a good one to have many of. Whether you want to trade or raid is down to personal preference: raids guarantee workable IVs, trades open up the possibility for luckies, netting you massive dust savings. Given that you've only been playing for a month I assume dust is a fairly large concern for you.

Machamp is top priority for fighting gyms and Tyranitar raids. You want several at level 30+.

Tyranitar is good for raiding Mewtwo and has long-term value. Advisable to get some from raids, they also provide a bunch of candy on catch unlike trades.

Like devshaw said, Eevee evolutions are good too. Flareon, Jolteon and Espeon are among the best of their types and Vaporeon is ok too.

Other than that, look at the lists of top attackers on this site and keep an eye open for weatherboosted wild ones with high CP, it's the easiest way to build your roster until you acquire more resources.

Back in my day you had to raid at EX gyms to get a Mewtwo. And call in sick from work to go to the EX raid at the specific time slot. And hope enough people show up to catch him! And use all your rare candies on him because he was so rare! And walk uphill in the snow both ways with no shoes or socks in the rain!

Obviously you may not need all the Mewtwo you catch, but it's advisable to catch as many as possible for the candy. Select your best and trade the worst to get more candy and other useful pokemon. Do you know how to check IVs?

Tyranitar is available in T4 raids. Getting ahold a couple of good Tyranitar with double dark moves is very advisable.

Depends on your raid scene.

If you're regularly able to get lots of trainers at each Mewtwo you go to, then there's no real need for you to get a Tyranitar. Those raids will 99% still be around when Mewtwo leaves us (Tyranitar has only left the raid rotation twice, during the Kanto events, according to what I've read here), so you can get your Tyranitar after, when something less useful than Mewtwo comes around.

If on the other hand, you occasionally need to try to short man a raid, doing a couple Tyranitar could help get you more Mewtwo overall by making you successful in those short mans. Also, if you have extra passes (e.g. you can't use up your free pass every day reliably due to work, etc...) Then definitely raid Tyranitar when you see it.

Mewtwo is a highly desirable tier 5. I suspect groudon or Rayquaza are coming up soon in the rotation and they're likewise highly desirable. Otherwise though, Tyranitar is probably more desirable than any other raid repeat right now. As for new raids, a few Gen 4 (dialga and palkia) are hugely desirable, while others probably aren't so much.

The biggest thing is to use what you have until you find something better. There are plenty of Pokemon that will never make a top attacker list but are still quite serviceable:

Ursaring
Charizard (even without blast Burn)
Venusaur (even without Frenzy plant)
Exeggutor
Nidoking/queen
Victreebel
Vileplume
Arcanine
Poliwrath
Golem
All eevelutions
Granbull
Houndoom
Sceptile
Blaziken
Swampert
Shiftry
Cacturne

And others. Obviously a lot of those depend on your biome, but find high level Pokemon with any ivs, evolve them, and battle away.

Tyranitar definitely, mewtwo's best movesets no longer accessible (and most of its current movesets are pretty specialist/inferior to other attackers of the same type, best there is left is psychic but its use is largely only machamp who likely wont be back for another month) they arent as worth it to go for unless you have a good Shadow ball mewtwo to put the mewtwo catch candy into, and Tyranitar's always been a good and reliable attacker for legendaries, and with the 5 gen IV legendaries that are weak to dark, when gen IV comes those tyrnatiar will be seeing a lot of use.

I wouldn't count on the trades for those rare pokemon, mewtwo's a dime a dozen now, unless it has shadow ball they arent worth as much as they used to. And with gen IV likely to come any time, a lot of current best attackers are threatened, of the current raid bosses only Tyrantiar's a safebet, if you need a machamp smacking squad, get some mewtwo for that but theres other alternatives like espeon that dont cost as much to get powered up

Since legendary raids are easy to do in your area, focus on doing them for the Rare Candy, TMs and golden berries.