Since many people have asked about what gold purchases to make first, I've decided to compile a list of them from top to bottom in the order that I believe is the highest priority to get them.
1 – 3rd hangar slot
This one should be a no brainer.
2 – 4th hangar slot
You can still function well without one, but if you don't have one, at best you'll be a liability to your team and at worst, you can make the entire team lose due to the lack of time one bot can give. Also, no decent clan will accept you if you don't have one. Any player in Silver league or above should have at least 4 hangar slots and if not, save up for one as their absolute priority.
3 – 5th hangar slot
Although not completely necessary in the majority of games, having 5 hangar slots allows you to carry games that would have otherwise been lost. It gives you more variability and firepower as well as more leeway in knife fighting due to having more bots. It also allows you to add in a good mid-long range robot without compromising your knife fighting power. Most mid-high league players have 5 slots, and they are essential for high league players (e.g Expert league). It is recommended to purchase 5th slot or to save up for it in Gold league and above.
4 - Mk. 2
Mk. 2 is a way for already stupidly good players to further improve their already stupidly good gear. It unlocks even more potential for weapons and bots. Strongly recommended for higher leagues.
5 - Boosters
Boosters (especially resource boosters) are essential with the new economy. With repair costs being very high, leaving players with very low profit, it is essential that boosters are used.
6 – Paint Jobs
These are not recommended but can make your robots look more threatening, act as a sort of camouflage..or make your robot more of a target (the latter only occurs in the lower leagues) However, if you're in a clan or already have all the robots and weapons you need/want, then treating your robots to a visual upgrade can be fine.
7 - Silver
One of the biggest wastes of Gold in the game. You need 250 Gold just for 500K Silver. Although you would need to play 9-10 matches for the same amount of silver (without boosters or premium), it is impossible to get 250 gold in the same amount of battles. Plus, why would you waste the hardest to earn currency on the easiest to earn currency?
Don't waste your gold on this unless you have all of your gear up to Mk. 2, a ridiculous amount of silver and boosters, a maxed clan, and every paint job in the game in addition to all of your slots. Otherwise, go ahead. Gold is useless to you at that point.
9 - Clan
Clans are currently the best (and only) way to link up with coordinated squads outside of connecting to facebook. Creating a clan costs 1500 Au, which can be farmed relatively easily. After creation, members can donate gold to the clan in order to increase its player limit. But at this stage in the game, it is much easier and more beneficial to join a clan. Creating one at this stage will most likely leave you with no members and no benefit.
- This guide is originally attributed to Strayed, however, it has been heavily edited since then.