Very good advice has been given for your situation in another thread.
You can view it here.Relevant info from the post by
Redfiend is below.
Beginner's Advice:
I left this for last, because this game is a marathon, not a sprint. Everything comes with time. By EXP calculations, even if you got the most exp you possibly could every day, it's still going to take months to unlock everything. This only makes sense after all of that.
Right out of the gate: You're going to have Rank 1 Lancer, Rank 1 Paragon, and if you did your first daily missions, rank 1 Juggernaut.
Lancer: RPG2 x2
Paragon: RPG 4 x2
Juggernaut: Autocannon 2, Autocannon 4.
Feel free to level these up as you wet your feet. Just don't commit to a Rank up yet.
V
Replace Paragon with Panther(275 A-coins), who starts at Rank 2(12 Energy). Throw Thermal Lance 6 or RPG 6 on Panther for the time being.
Juggernaut Rank 2 is the priority for rank up so it has 8 energy and can actually fight properly. Replace the auto cannons with RPG 4s, or Plasma cannon 4 if you intend to run Shadow later.
While leveling Panther and Juggernaut through rank 2, plan on setting credits aside to buy Killshot. It's very easy to get it in the first couple of days with the upcoming Tournament guide.
V
Replace Lancer with Killshot.
All of your Bots are now Rank 2, and all of the bots can be upgraded at the closest convenience because they are all end-game viable.
While you're waiting for Blueprints and leveling them up, Pick up Plasma Cannon 6(might take a few days to unlock it, but so will getting this far). Panther can do well with these because it can trap bots with it's wall.
When Killshot reaches rank 3, it can get RPG6 unless you want to shell out the premium currency for Javelin 6.
When Panther reaches Rank 3, it can wield double snipers(16 energy). As the best counter-sniper, it's heavily recommended that you get used to dealing with AimBot AI's.
When Juggernaut reaches Rank 3, it can inherit the Plasma Cannons that Panther was holding.
This three bot hangar is as solid as you're going to get within the first week or two of playing the game. From there, you can start thinking about the next mech you'd like to add to your hangar:
MD for keeping the dumb AI from being completely useless, and extra staying power on a quicker unit.
Shadow for stealing everyone's bacon, and being as absolutely insufferable as you can possibly be at enemy flanks.
Ares for another tank that's better at opening a match due to better ground speed.
Or do you really just hate Juggernauts and want a Guardian?
At that point, it's all up to what you want to do.
EDIT: I think you did already read this. I just keep my Paragon at Rank 2 and bring him out to complete any daily challenge that calls for the Paragon. Otherwise, it sits on the sidelines.