When you decide to invest in Bitcoin you need to go for it so that you can make as much money as possible with it.
Buying bitcoin was it one or more is always good for profit
it is not short term investment it's long one
It is a very long long long term investment if it is just 1BTC. It is a good investment but it is better if you have more than 1 BTC. But you can invest that 1 BTC on investment sites and earn more BTC so you will have more bitcoin to hold. In time if you keep re investing your bitcoin, you will be financially free.
I guess that is going to be insufficient if you are targeting to have a long term investment. Because the higher investment you are going to put for a long term investment then the possibility of higher returns are there. So if you want to invest for a long term one, make it higher so that there are no time to be wasted.