I use EV ZLX-12P for monitors. They cost a lot less than the QSCs and can get similar levels. Side by side with my K12s they don't have the same clarity, but bang for the buck you can't beat them.
Unfortunately that is far too little of a budget to buy anything at all. The minimum I'd recommend for a pro mobile DJ would be 2 EV ZLX 12's: http://www.amazon.com/Electro-Voice-ZLX12P-Two-Way-Powered-Loudspeaker/dp/B00CE0VLXO/ref=sr_1_1?ie=UTF8&qid=1436975253&sr=8-1&keywords=ev+zlx
If doing a bass/dance heavy genre(s) like EDM or Hip Hop you will also need a Subwoofer.
Agreed. Go to a Guitar Center or a shop near you and listen for yourself. American Audio are as bad as Pyle, if not worse. That being said, you know your audience and what you're trying to do. If you want to really disappoint your clients, then by all means, reinforce the stigma of a bedroom DJ and go do a gig with those things. Otherwise, if you want to do it the right way, Rent quality speakers and do a few gigs until you have enough to drop $800 on an entry level pair of professional speakers, like the EV ZLX12Ps.
I'm aware they won't last long. I can't afford to shell out more than $350 right now for this: https://www.amazon.com/Electro-Voice-ZLX-12P-2-Way-Powered-Loudspeaker/dp/B00CE0VLXO
Is one of these worth it for the parties I'm doing?
I prefer JBL, the EON 615 is a good choice.
I would also look at Electrovoice ZLX series speakers:
However if you are doing Dance music I really think you'd be better off with two 10" + a subwoofer rather than two 15".
This PA system kit is pretty popular as a good value for the money kit for mobile DJs: http://www.amazon.com/B-52-MATRIX-1500-1200-Watt-Active-Speaker/dp/B00OJ97BD2/
edit: Here you go: http://www.amazon.com/Electro-Voice-ZLX12P-Two-Way-Powered-Loudspeaker/dp/B00CE0VLXO
http://www.amazon.com/Behringer-XR18-18-Channel-12-Bus-Digital/dp/B00UC16Q2I
glad you showed up here. get powered speakers. Look at the EV and JBL powered stuff. It has processing in it, does a lot of the work for you. Look at the EV powered stuff for value. They are proven. Good value and they work and they're cheep.
Mixer? what can you handle? Are you a computer person with a tablet for control? Behringer digital ?
cheep cheep cheep. you could get two powered speakers and a digital mixer new with warranty for $1500. total.
Behringer iNUKE NU3000 Amp OR Crown XLi 800 Amp
JBL Control 28WH - White speaker pair no non no no no no this stuff is junk. Control 28 are airport or fern-bar speakers. get powered speakers, in case you forgot. The real question is "what kind of engineer are you?" because with digital mixer you will have a ton of control. Do you know what to do with it?
Depending on how big the room is that 30 people will be in, how loud you want it, and how much bass you want, the EV ZLX-12P and 15P are great options. The 15P will have more bass, but it is also more expensive. Both have fantastic sound quality and are very loud. I've used 2 paired with subs for a high school prom for 500 people and they were perfect. Granted they were almost maxed out, but this just gives you an example of how loud they are. They have a 3.5mm (headphone/aux) jack on them which would allow easy connectivity of a phone or laptop, and you could daisy chain one speaker to the other if you wanted to use two with a simple XLR cable.
Speakers: these http://www.electrovoice.com/product.php?id=2583 also shown here http://www.amazon.com/Electro-Voice-ZLX12P-Two-Way-Powered-Loudspeaker/dp/B00CE0VLXO or these http://usa.yamaha.com/products/live_sound/speakers/active_speakers/dxr/dxr12/
Mixer: This http://www.sweetwater.com/store/detail/XR18 or this http://www.sweetwater.com/store/detail/XR12 Intoxicating video https://www.youtube.com/watch?v=CrlSyAD-dVs
Mic cords: this http://www.bhphotovideo.com/c/product/517432-REG/Whirlwind_MK425_Accusonic_2_XLR_Male_to.html or this http://www.chucklevins.com/products/whirlwind-mk425-microphone-cable-25.html
Mics: I am a traditionalist. Shure SM57/58. Nothing else to talk about unless you are micing drums and I do not think that is your concern at the moment.
Do-it-yourself sound is like a garden. It happens over time.
(friendly edit here)