I think the most important tips for beginners are around resource management:

1. Don't upgrade your lower tier mechs much. Maximum one time. Otherwise your lower tier mechs will start facing very powerful opponents.

2. The lower tier mech that benefits most from one upgrade is lancer. Its default energy capacity of 4 is useless except in the first few games.

3. Instead of upgrading, save your resources (credits and acoins) for buying mechs and weapons to unlock new tiers.

But Be extra carfull If you spend money on this game. Because once you do. The only thing you'll see is stuff for sail and when you buy any mech/weapon. You will start to notice that what ever you buy you will see less of the blueprints drop. and more of what you don't have.. and the only way you'll be able to see the blueprints . Is with real money. But the choice is all up to you ifyou buy, And a nother thing. Do not and I mean do not belieave when anyone " Crystal Drew " say that the items ar just novelties and a way to level up faster.  Thats just a way to get put in higher level players and have stronger weapons then you will have. And almost all the player/people you playing with are mostly bots. I can give you the list of all the bots on the game. The bots will be coming at you with higher level and and updated mechs & weapons. Thats a tactic move the game dev's put on everybody to get them to but mecks & weapons. Just read through out the forum. get familiar with it read it every day for a lil time so that you know whats going on. Not the discord forum . But this one. Discord forum on meck arena is kinda funny . Not liked by many and loved by others.Trust in what I'm saying. You'll see everything I said come in moments notice. 

Also I forgot to add. If you don't see a clan tag. Just think of them as being bot. More likely that they are. Unless you see there names in the recommendation column

Dont  spend on useless weapons, save credits and acoins. Especially acoins. I have been saving for 6 months and still can't get my hands on surge. The most wort it are storm racks, revokers, pod guns. 

If you're going to spend a coin, get legendary pilots to match the weapon type you prefer. Start earn xp to max them as soon as possible. They increase your mech hp and appropriate weapon dm.

Also you can move them to new mechs, so every battle you fight is upgrading your pilots, thus your mech and weapons. And when you upgrade to a better weapon system or mech the increased hp and dm move with you.

And use the newbie promo 

They only give you plans and skins for the mechs and weapons you have. If you intend on spending real money, buy legendary and turn down any free mechs or weapons they offer that aren't legendary otherwise you'll get plans and skins for mechs and weapons you'll never use.

By the same token if you're strictly f2p, don't be tempted to get mechs or weapons you won't use in the tier you are in to advance to the next one, plan it so you can advance with the smallest inventory possible.

RuFFles on YT should help a lot there, he's got tons of stuff about it