Hold your Bitcoin,now is the best time to hold it,it is now in the bearish period and if you want to invest in altcoin check the coinmarketcap and invest on coins within the top 10,to secure your profit.
Holding won't multiply your bitcoin, it can only increase or decrease the price value of your coins. OP wanted to increase his BTC and he thinks that ICO is one of the possible way to multiply it.
The suggestion given by the first people who replied before me should be considered. Scam ICO are very rampant ever since but it is much clever to the point that they will make it look very legit with people behind them being revealed. So better do a thorough research on the project, especially the declared people behind and see it for yourself.