Well, it depends on you. I mean I've seen people invest practically nothing and stil earn it big in crypto currency, I've seen people bet big in the wrong time and lost ot all and seen people bet small at an oppotune time and made it big in the game. It is all a matter of what you are risking to invest and reading up to decrease the risk.
No it is not necessary but if you have big investment then it is much better. You can buy bitcoin in big quantity because the price is quite good for new investors and will make big profits when the price rises in the future. It is risky but also profitable. You should take some risks to get big profits from your investment. Bounty and signature campaigns will give you coins for free.