It is a general rule of thumb that you only invest with disposable cash, not money you may require for your vital needs.
Also, avoid purchasing stocks with the cash you will need within the next five years at least.
This is because while the stock market generally rises over the long term, it will constantly post sharp drops of 10%, 15%, 20%, or more without any warning.
One of the worst positions you can find yourself as an investor is having to sell stocks during the down periods to recover funds for urgent needs.
Ideally, purchasing stocks when others are selling theirs is conventionally advisable.
Finally, only invest with sums you are willing to part with and be mindful of your appetite for risk.
The amount of funds you should invest comes down to the number of shares you want to buy and their prices.
Keep in mind how much you might need to spend to diversify your portfolio properly.
If you cannot purchase your desired high-growth stock in whole, you can explore the options of fractional shares.
Fractional shares enable you to purchase fractions or parts of a stock.
For example, if a high-growth stock is valued at $500, you can purchase %100 worth of the stock, giving you a fraction of the share worth 20%.
Most online brokers like Robinhood and Fidelity render fractional share services.