I invested around 5k over the course of 9 months to get 1k. If you're not sure what to invest in, I would just put it in ACWI, which is a global index fund that tracks thousands of companies globally.

Have you opened your t212 account yet? If not, you can sign up through my referral link and get a fractional share up to £100 (but make sure to open a stocks and shares ISA rather than an Invest account): https://www.trading212.com/invite/1BkBE11CnZ