Really for LR, the only tip is "learn how everything works". There's no easy way to beat the game without mastering most of the stats.
I would suggest focusing on boost hopping, avoid Narrow and Deep and Special weapons (they have very small lock ons), try to use EOs or dual wield so that you can increase your damage per second. Make sure all your parts work together, also.
For heat and drain:
Total Cooling - (Heat Emission Value + Boost Heat) * 2 = How much heat you will produce while boosting.
So if you have 4000 generator heat and 4000 boost heat, you need 16000 cooling or you will overheat while boosting.
A solid newbie build VS ACs would need to have high stability, lots of easy to fire weapons (no aiming required, wide lock box, lots of ammo) and good turning speed (to avoid losing track of the enemy)
It would be something like:
Head: H81S4 (High stability, no radar needed because you have a back radar)
Core: C98E2 (High damage EOs)
Arms: Lemur2
Legs: Gavail (High stability, high turning, low stationary drain) If you need more defense, use 92S3 or 94A2
Booster: Vulture2 (average stats overall)
FCS: F69 (widest FCS)
Generator: G91 (low heat, high output)
Radiator: Linden (high forced cooling, low drain)
Inside: None
Extension: 92RM3 (high damage, lots of ammo)
Back Unit R: Satyros (high single-shot damage, more likely to hit. Magoraga is a better choice against enemies with anti-missile systems)
Back Unit L: Siren (Fast scanning interval, low weight)
Arm Unit R: Pixie2 (lots of ammo, decent damage output)
Arm Unit L: 79M2 (high damage output. Use Fairy if you need to save weight)
Use both machine guns and EOs when they're in front of you, switch to missiles when they're too far away, behind cover, or not on your screen.
Also make sure you customize your control scheme. Good idea is to put movement on R stick and turn/look on L stick with weapons and boost on triggers.