I suggest that don't play immediately, playing with bots and also training with other legends is good. When i first played Brawlhalla i played with bots first and training. I'd rather suggest practicing every string or combo for 5 mins so you can master it. Then you could be a better player. Note:
Dair = Down Air
Sair = Side Air
Nair = Neutral Air
Ssig = Side Signature
DSig = Down Signature (I'm not sure if this is really a thing)
Nsig = Neutral Signature
Rec = Recovery
NLight = Neutral light
DLight = Down Light
SLight = Side Light
And spamming Signatures such as "NSig, Ssig, DSig" is very annoying move and most of the beginners do that to knock them out of the platform.
GC = Gravity Cancel (Shift wait a few seconds and do whatever attack you want, And you must not move anywhere wherever you jump and shift. You must stay still, attacks can be done with Gravity Cancel too.)
Tip : Sparring with pro players such as Diamond players, Gold and Plat players. Players with higher elo will generously teach you combos/strings you need to know. Watching in youtube is a great idea.
I hope this guide will help you for being a good/better player!