Decrease as it is new and strong rival to btc.
Without trading or investing that target is not achievable at all, because 7 btc cannot make 10 btc just by holding and it does then it would really take a lot of time as the price of bitcoin rises slowly not fastly.
Trading is the right option to achieve that target but investing 7 BTC is a big amount, and if you face loss then it is big loss, so i suggest to invest some amount of money in trading and wait for while and then invest again in trading.
Yes I think its better to start trading with 2 btc and rest 5 should be kept safe as even 2 btc is good amount to start and you can earn descent profits from it.