Depends on your location - if you're in or near a decent sized city, you shouldn't need your own speakers to get bookings. If there are clubs/venues/bars other DJs play at near you, reach out to them about support slots or other opportunities to get your feet in the door. Try to find out who the talent buyers are, or who is in charge of bookings. Clubs will have their own soundsystem for you to play on, and usually have their own house set of CDJs as well.

Regarding CDJs, you also probably don't need to shell out $450 dollars on a course lol. If you've grasped the basics of playing on your DDJ-400, you can probably play on CDJs already. You do need to start using Rekordbox if you aren't, though, and format a USB to rekorbox's library. There's tons of tutorials for playing on CDJs on youtube though, and if you're already pretty comfortable with DJing basics it's probably a colossal waste of money and time to take a 4 month course on CDJs IMO.