u/levitas

General tips:

Get stuff that you will play (if you don't play it ever then you get zero value from the free mech)

Get stuff that is expensive (a locust pb or fire moth aletha should not be picked because they are dirt cheap. Heavier mechs tend to be more expensive so if you want a pb and a dante, get the dante for free and use lootbag mc on your pb)

Try real loadouts in testing grounds for every mech you are considering before you redeem. You can go to the grimmechs database and copy a build code, then import it into the mechlab and take it into testing grounds.

Take your time deciding. Maybe in a month one of the two mechs you were choosing between goes on sale and you can pick it up for MC and the other one as a redeem. Just don't forget to redeem!

You get one light/medium, one heavy, one assault, and one legend pack (includes all the pack stuff like mc/warhorn/etc)

Here are the mechs I think are worth considering for most people:

Lights/Mediums:

Veagle Rival - masc poptart with great quirks

Shadow Hawk IIC dante - flexible, at least 3 good loadouts. poptart with heat quirks

Black Lanner Bellonarius - essentially a comp pick. you get an energy hardpoint instead of ecm in head. good though.

Viper Scaleshot - poptart with srms that have longer than usual range

Shadow Cat mishipeshu - for the right arm, you get an extra ballistic hardpoint

Uziel Belial - 4lppc 2mrm10 poptart with hyperspeed mrms. very fun.

BlackJack Arrow - DPS or poptart, either is great.

Urbanmech Street cleaner - urbie poptart, running speed quirk

Jenner Oxide - srm bomb, doesn't jump, still good and pretty tanky for a light

Kit Fox Purifier - 4 high energy mounts opens up a lot of build options for the mech.

Heavies:

Marauder Blight (lgd) (dakka) - crit immune with good quirks and hitboxes. A top performer in QP

Marauder BH2 (snubs ac20 + slas or lasvom) - Versatile mech, very solid.

Mad Dog Bandit (2uac20) - One trick but it's a really good trick.

Orion IIC Skoll (3ppc lb20/ac10) - Masc + good PPFLD at range and bulk.

Grand Summoner Talon (fast dakka 4pac4 2plas) - high tight mounts, supercharger lets it go relatively fast.

Timber Wolf Howl (lgd) (brawl or ATMs) - Versatile battlemech (NOT omni - no pod mixing) with masc, jjs, good hardpoints, good quirks.

Archer Tempest (lasvom with ecm and range quirks) - Bit of a sleeper IMO. Great new quirks and it was good before.

Quickdraw Desperada (lgd) laser poptart - Built like a steakhouse but handles like a bistro. Short laser burns are perfect for poptarting, and quirks help.

Cataphract Naomi (lgd) poptart with ecm - the better butterbee. ECM, JJs, you can do MRMs and lppcs, MRMs snubs, snubs srms, lasvom, even lock ons.

Catapult Ferroblast (lgd) (4lac5 2lppc or snubshot) - There is no faster heavy in the game. Very fun, but you do have to pick your battles because you'll lose 1v1s against things your size.

Assaults:

DWF-UV (enables dakka builds on -WM especially) - 2B on each arm is a big deal. Enables 8lb2/8ac2/5 or 6AC5+PPC of choice style builds on the -WM (for DPS) or -C (for ecm+JJ)

HGN-HM (no jj shake, big jj quirks) - very unique and good poptart for QP. Convergence is poor but genuinely it is fine. Great mech.

STK-WU (lgd) (dakka) - crit immune with great hitboxes and plenty of firepower.

EXE-B-C (lgd) (dakka) - Another dakka option, shares omnipods with other exes but with fewer JJs and a small engine it is built for dakka.

KGC-A (lgd) (ecm dakka) - UAC10 HSL and ECM makes it the most comfortable king crab in QP.

Bullshark VK (ideally get this in the legend pack and you'll also get -WG as a 2 for 1) - VK is still the best platform for railgun. Perfect convergence long range 40 PPFLD + splash but long cooldown. Bring 2PPCs with it and stagger fire (it will ghost otherwise) for even more output.