Grabbing upgrades in levels is great. Shields can protect you, multipliers can of course increase your score, magnets make it easier to grab extra currency, it's great. But those upgrades get even better if you spend some money at the shop. You don't buy upgrades, but instead you can pay some cash so they work better and for longer when you pick them up on a run. The price will increase each time, but they're well worth spending your hard earned currency on, especially since ultimately, it'll make it easier to earn currency with each upgrade.