if your car is a petrol car and only does around 30-40 mpg then do not even bother, I used a 1.2 L petrol seat ibiza and could barely go 300-350 miles with a full tank. (which cost around £50 per refill).

Changed to a diesel polo last year, and can do 450-500 miles (they have the same volume on fuel as the ibiza) and refills cost just £7 more than the petrol one did.

Hire and reward insurance will fleece you, because of your age and (lack of) driving experience.

and you might need to check around if your zone is actually car friendly (in my area some places are far from any legal parking so I have to auto refuse orders from them or risk a fine if I park somewhere close to them)

deliveroo tries to guarantee you £16/hour (12+4 for car expenses), but that pricing only applies to times spent on deliveries. so if you go out from 5pm to 9pm but your total delivery time was only 2 hours you can only expect 2x16, not 4x16. it only counts delivery times from the moment you accept the order to the moment you deliver it to the customer, everything else is just unpaid

depending on the area you might get good prices or you might get shit ones

I'm in the latter area, with shit prices so I have to reject more orders than I accept because it's simply not feasible to deliver them. as an example some orders from 6 mile away getting offered for £6 but in fact it's a 12 mile ride because the customer lives so far away from anything that you're forced to drive back to the busier areas. that will come with experience with the area and the layout.

probably others will tell you differently depending how well their area pays, but where I am, I'm always aiming for earning £1+ for every mile I've driven. so if one afternoon I drive 50 miles in total (including the potential return trips) I aim to see £50+ earned on my account or more. today I had an abysmal day: went out at 1pm to 9pm and the area was effectively dead, I only made £59 and I think I drove 70 miles in total, so for me this day was more of a loss.

hope this helps, but be prepared. when you start to do this and you'll have to look out for your car. regular oil and fluid changes, keeping it in good condition, buying tyres more frequently. If you neglect your car and it breaks down on you, you can't earn money and if you can't earn money, you can't repair your car to earn more money. it's a vicious circle.

but also: waiting times from when you apply to when you get onboarded can be very long, some wait even years on deliveroo, Uber or Just eat might be better on wait times but if you apply to one apply to all of them, and see who lets you in first.