Once you've fully unlocked the Basics on three variants of a chassis, the requirement for three full Elite unlocks to get to Master switches to "in the same weight class." So, if you didn't know, that means you only have to get basics on the sub-optimal variants. You may well know this, but sometimes people don't. =) Also be sure to buy Artemis for any Streak-armed 'mechs, since it affects lock-on times (this will eventually be fixed, I'm sure, but right now, abuse it - you can be certain the other guy is.)
As for which chassis to get first - it depends on what you're looking for. The Raven spreads damage better than anything in its weight class but a Spider - and it carries more firepower than a Commando. Commandos, on the other hand are
far more maneuverable than anything but a Locust. This is because they share the Tiny movement archetype - the only two chassis in the game thus far who have it. So while Ravens can effectively carry much heavier arms, a Commando can turn on a dime and still hit fairly hard with light-weight weapons.
Similarly, a Raven has birdy-wings rather than arms, making it much more difficult to hold locks on evasive targets, or to focus your damage while presenting a high-deflection shot to your victim - ecactly like the Jenner you've already learned. Conversely, while the Commando carries fewer/smaller guns, it has true arms like your Spider, and can hold locks and pinpoint damage more effectively while making itself a difficult target.
Finally, while the Commando's small size makes it practically impossible to specifically target a weak torso/arm, the Raven has very good damage spreading on its hitboxes - and substantially more durability. This means that while the Commando will be harder to hit, a Raven will stand up better to other lights and streak boats, as well as being more survivable against large-bore autocannons and PPCs.
So it comes down to what you want to buy first: a fast,
very nimble assassin, scout that specializes in zipping around enemies to disrupt them with hit-and-run attacks, or do you want a more robust chassis that can effectively carry heavy energy weapons as well as light-hunting armaments - but with less maneuverability and speed?
Do you want the Commando, or the Raven?
Edited by Void Angel, 22 January 2014 - 10:47 PM.