There is some truth there in what has been said.
Most new people look at the purchase of a firearm to be "Hey, I have a gun" without realizing what they need the firearm for.
That is like buying a car, just to have a car, and not looking at why it is needed in the first place.
Your budget limit of $300 will not buy a firearm that could be used as an heirloom later. There may be a couple of firearms available for that price, but most will break, have accelerated wear, not have aftermarket parts available (like magazines or holsters).
"A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed."
Life Member NRA
Life Member NAHC
Former President of the ECPT (Eifel Combat Pistol Team)