You don't need anything to train, just head to the gym in your gym kit. But here's a few items that can make your sessions more effective and comfortable.
What belongs in your gym bag
1. Gym gloves
Gloves are definitely optional, but there's no reason to make your hands uncomfortable during training and calluses are not "manly".
2. Lifting straps
When to get them: Consider straps when grip becomes the limiting factor on heavy pulls, dumbbell rows, or shrugs. You don't want your grip to be the limiting factor preventing you from achieving hypertrophy. Don't forget to add in some grip exercises to make up for the reduced grip training you'd otherwise get.
3. A secure place for your ring
This is a weird one, but rings can catch on equipment and become uncomfortable during training. Remove them before training and keep them in a zipped pocket or secure case rather than leaving them loose in your bag. I actually have a small clip on my water bottle to keep my wedding ring secure.
4. Water bottle
Obviously a requirement to stay hydrated. Don't rely on going back and forth to the water fountain.
5. Towel
Bring a small towel to mop up sweat, again not optional.
“Bring gear that removes friction from your training, not equipment that distracts you from hitting your reps.”
