The first and most obvious tip i'll give you is
a) become top score
b) pray to RNGesus and Lootcifer that you get good Loot

The protonium crate has the best overall chance of getting Epic & legendary items, but that doesn't mean you can't get good items from other crates too.

remember what gives you most score
1) capping towers
2) healing
3) dealing damage
4) kills and assists give equally as much score

Different gamemodes give more items per crate

1. Buying crates always give 8 items per crate premium or not
2. On a 24h cycle you'll get a daily crate that increases in rarity if you play several days in a row, starting at rust and ending at protonium(staying that way until you break your streak). This crate gives the same as a battle arena crate.
3. Team Deathmatch and The Pit gives you 3 items per crate
5. Battle/League Arena both gives you 4 items per crate
6. Single Player crates stack, so you get both a rust and bronze crate. 1 item per crate
7. Elimination gives 2 items per crate

Having premium will always give you twice the amount of items(exception is crates bought that always give 8 items) and all items in the back row of crate are premium items.
So Battle arena gives 8 instead of 4 Elimination gives 4 instead of 8 ect.
If you're an active player it's worth more to get premium than to simply buy crates.
Numerous people have made forum posts claiming they didn't get their items when in fact it was in the back row, don't be like them.

Stuff you need to know:

1) Protonium crates can never have common(white) items
2) You recycle items at a 10%-30% return rate, so don't do it.
3) You have a higher chance for rare items if you play at high(1750) cpu levels
4) rarities are common(white), uncommon(green), rare(blue), epic(purple) and legendary(yellow)

Here comes the most jewish trick FJ ever pulled:

Since all wepons are flattened, the whole "rarity" thing doesn't mean ♥♥♥♥♥♥♥♥♥ at all.

Uncommon wasp SMG
Damage Per Second: 60 768
Super rare epic SMG disintegrator DPS: 79 001
Energy to damage efficiency(wasp): 205,33
Energy to damage efficiency(disintegrator): 143,22

as you can see here the insignificant wasps who costs 10cpu only have a bit less damage and much better energy efficiency.

and out of the two energy efficiency is a lot more important, it's basicly ammo for your gun and once you run out you're going to do half(39 500) as much damage with your disintegrators.
Wasps can't run out of energy, they don't consume enough.

The Moral here is that you can do exceedingly well with normal common wepons and don't actually need legendary missiles and shotguns to do the work. In fact thoose wepons are actually really weak.

This is where most people have problems and where you need to think it through the most.

First and foremost; God gave 100 garage bays, i suggest you put them to good use.

1) Sell as few items as possible. Wasp SMG's per example only have a 20% sellback value as they cost 400 robits and sell for 80 robits.

2) don't settle on making one type of robot. If you got a mech leg save it for a future mech bot, if you sell it you'll regret it later. Put your garage bays to use.

3) Give yourself a threshold of how many of each item you want. If you say you want a minimum of 20 wasp SMG's and then sell them when you get above that amount you'll gain some robits without having to buy new ones if you want to use them later on.

4) Re-purpose items. You can only drive one bot at a time, the ones in the garage don't do anything. This means that you can "borrow" some expensive parts such as guns and movement from other bots. One set of disintegrator SMG's can be switched around to the bot you want to use, thus you'll save money and have more bots available. Don't try and put a legendary power module in every bot.

5) blocks are a cheaper and better alternative to electroplates, if you're short on cash use them.

6) one good bot is better than many bad ones, but don't be afraid to experiment. Failing at something is the first step to being sort of good at something. Put your parts to good use.

7) Have fun while collecting parts. If you make it a chore it'll seem to take forever. The worst offenders being thoose who grind in singleplayer for 4 hours straight, don't do Singleplayer folks.

8) Exploit free premium codes, FJ gives them out from time to time. If you ever felt like playing do it on such a glorious occasion. Also remember to paint your bots as they stay coloured until you change them.

9) recycling cosmetics is a great way to earn yourself some extra $$$

10) wait until you really need something before you recycle, your items aren't going anywhere. More than once people(totally not me) have recycled all items after battle to buy something expensive such as a power module, only to get a power module in the crate when you're at
140 000 robits.