As all of the SD cards I have right now are used for my cameras.
Also I am only 13 - I can't really afford to buy SD cards. I know that might sound stupid, but to get a class 10 SDHC card with a reasonable amount of storage, that can cost £15+ who only gets £5 from a paperround a week, it can be quite expensive.
I fully understand. However you only really need something like a 4Gb Class4 SDHC or micro-SDHC card + adapter to start with, especially if you already happen to have a spare USB flash drive about. You should be able to find 4Gb ones from, for example, amazon or an amazon store for around £5 or less if you're lucky. Many of mine are Kingston brand and I've had no problems with them.
Still running Raspbian Jessie on some older Pi's (an A, B1, B2, B+, P2B, 3xP0, P0W) but Stretch on my 2xP3A+, P3B+, P3B, B+, A+ and a B2. See: https://www.cpmspectrepi.uk/raspberry_pi/raspiidx.htm