For a new racer at an “advanced” age, the rib protector is probably the most important piece of safety equipment because it’s the most likely injury you could have (don’t go cheap on this). A lot of people in the sport go through rib related injuries and they are miserable (voice of experience). IMO, the neck brace and chest protector are a question of how risk adverse you are. I started with a $400 Leatt brace because I was planning to do high speed road course stuff and I felt this was necessary but I found myself doing only sprint racing and am comfortable with a foam donut. I have never worn or considered a chest protector, elbow and/or knee pads. I did wear one elbow pad when I was racing shifters as my elbow kept hitting the motor.
Outside of the safety aspect, I suggest spending a little extra on gloves and shoes because of the durability factor. I started off cheap and found myself replacing these items in less than 6 months because they fell apart (I now run Sparco shoes and gloves). A cheaper suit should be just fine for a while as they don’t take too much abuse. A M rated helmet should work just fine unless you are planning to test this at speeds higher than what a typical motorcycle incident might happen at.
In the end, buck up for the rib protector and then go with what fits your budget and makes you sleep better at night.