An apprentice in his first six months doesn't know what he doesn't know. He'll come in with a list someone gave him that includes a $300 puffy jacket, $80 in safety glasses, knee pads, a tape clip, a leatherman, and a back-support belt. We try to talk him down. Most of that list is what a fifth-year journeyman owns. Not what a first-month apprentice needs.
Buy first, no questions:
Boots. Already covered. Thorogood 814 at $230 or equivalent. Don't cheap on this.
Two pairs of work pants. Carhartt B01s at $55 each, or Dickies 874 at $35 if budget is tight. Two pairs is the minimum to maintain a wash rotation.
Three or four solid-color work t-shirts. Carhartt Heavyweight Pocket T at $20.
A leather work belt at $30.
One pair of leather-palm work gloves and one pair of nitrile-dipped knits. $30 total.
Wait on these:
Knee pads. Wait until you actually need them. Some trades never use them. Buying them on day one means they sit in your truck and get crushed.
Tool belt and pouches. Apprentices are usually given tools and don't need a personal pouch for a few months. Wait until your foreman or journeyman tells you to get one.
Insulated jacket. Wait until November. The apprentice who buys an insulated jacket in March and doesn't wear it for seven months is going to wear it once and not like it because the fit changed when he gained a few pounds, and now he's bought a $200 jacket twice.
Bibs. Same as jacket. Winter purchase.
FR-rated gear. Only if your trade requires it. Don't pre-buy.
Tools beyond what your job provides. Apprentices wreck tools. The shop's tools are the ones to wreck, not your $80 personal hammer.
What to never buy as an apprentice:
Branded merch t-shirts in lieu of work t-shirts. The branded t-shirts are nicer cotton and they wear out twice as fast on a job.
Steel-toe sneakers as a 'beater' option. Either you need a steel-toe or you don't. A halfway boot is a waste of $80.
Back-support belts. The medical evidence is mixed at best, and most foremen don't want to see them on an apprentice anyway. Build the back through the work, don't shortcut it with a brace.