You have to target at least 1 BTC for the start but in the long run you will realize that 1 BTC is not enough, I know not all of us can afford to raise 1 BTC for the future investment because that is still a big amount of money for the majority but for future investment I would say it would not change your life.
yeah you cannot do much with bitcoins, and if you are hoping to get rich with 1 btc then it will never happen as we don't know what value it will hold in future.
It also depends on what we do. every thing is done with confidence, work hard, have high spirits, and optimistic will surely generate something outside of his or her dreams. Since God prefers someone who is willing to bend over backwards to realize all the dreams, goals, and expectations
If you have 1 btc then you can always use it in trading and if you are lucky and if you make smart moves then you can take your 1 btc to higher level in future.