The amount of power you radiate is irrelevant, there is no real difference between 25 watts and 50. There is no reason to turn down the power.
When you become a ham, you will want everyone to hear you and you will want to talk to everyone. NOT JUST THE LOCAL GANG ON THE LOCAL REPEATER.
THAT IS JUST USING THE REPEATERS LIKE A TELEPHONE - WHICH SHOULD NOT BE DONE ON AMATEUR RADIO.

BUY yourself a power supply..
I have picked up many Astron RS 20A power supplies that worked at hamfests for about $50!
They are everywhere!

A good Deep Cycle battery will cost about $100 +
There is only about 4 manufacturers in the USA, one is DECA, I have a friend that does support work for DECA. They make the batteries for SEARS, WALMART, AUTO ZONE etc....

A good Deep Cycle battery charger is going to cost you about $70.00
It is not to your benefit to spend $170.00 to use a battery when you can buy a brand new Astron RS 35M for the same amount of money.

YOU are a HAM now!
The TECHNICIAN class license is not a stopping point, but a starting point.
YOU are going to need the larger power supply to operate a HF transceiver, which you will need when you get your GENERAL class license.

Remember - we are here to learn, when you stop learning, you stop growing.
Advance as far as you can go and you will go places in amateur radio.
Give back to amateur radio when ever possible - becomming a VE and becomming a ELMER - after you have been trained is a good start..

FIND yourself a good ELMER and have him / her show you the proper way to operate.