Reply to Helping out my son

So my son is really getting into this entire DJing thing. He's been saving up his money and bought himself something called the iDJ3??? We'll I have been doing some searches and couldnt find anything as far as speakers go. He was able to do this on his own so the least I can do is support him and get his speakers. My thing is I dont want to drop to much money into it if he isnt going to stick at it. So does anyone have any recommendations? And please break it down into dummy terms for me, I have no idea about any of this. I'm just a dad trying to help out his 15 year old son.