The surprising value of bitcoin makes it difficult for us to invest, maybe altcoin can be a solution, investing in altcoin is the right choice, but if you buy bitcoin now, you may be surprised for a few more months, as bitcoin values will go up 
I think you got it wrong, you just invest like 100$ for example it does not matter if it is 0.01 bitcoins or 0.001 bitcoins, if bitcoin makes a x2 in 2 months then you have 200$ it does not matter the price of 1 bitcoin.