Look for speakers that have lower ohm ratings. Be careful to check the power wattage of the speakers. If your speakers are not rated at the same or more wattage than your power amp, you can blow the speakers. Placing the PA speaker on a stand during a performance will also make them sound louder. An elevated speaker will sound louder because the floor will not absorb the sound as much.
Speaker stands can be expensive however.
You can eliminate the need for speaker stands by putting the speakers on low cost milk crates draped with black fabric. When buying mics on a budget, stay away from mics that need a preamp or phantom power. Preamp or phantom power systems cost money you can't afford to waste. Phantom power mics usually sound better, but in a live gig situation most audience members will never be able to tell the difference. Make sure you buy a mic that can take a beating.