ThreeProng
I've Got It
I wouldn't recommend giveaways. If you're getting big and you want to REWARD your subs for their support then by all means yes do a giveaway FOR THEM and some new subs will also come in when they see your dedication. However being small and doing a giveaway just for the sake of gaining subs is counter-productive. This is because everyone will come to your channel for a shot at getting whatever prize you're offering, sub or whatever they have to do to enter, then unsub when it's over. If they don't unsub and you do gain a couple, since they only came to get a prize and were not interested in your actual content they will likely not watch any of your other/future videos.