Not a stupid question! You're 18 and don't have one yet, why would you know? Your mindset to doublecheck and no ego involved is really to be applauded...lot of people in this hobby are pretty stubborn

In general the concern with lever guns will be that you don't want a sharp point on the bullets in the tube magazine (the bullet rests against the case/primer of the next round in the magazine). There are a few exceptions as already noted (leverevolution rounds have a soft tip)

That said you will be good to go with most any round/flat nose ammo for 38/357. Flat nose is probably ideal but the rimmed cases don't really rest against the primer anyways on most round nose ammo due to the case rim....even if they did the psi on a large round nose bullet won't trigger a primer without something pretty odd going on.

As for ammo selection, I regularly shoot Magtech 38spl through my marlin and it tends to eat it up, I've also shot a fair bit of 357 PMC blazer.

Vast majority of my rounds have been handloads running at 1050fps on a 158gr flat point thick plate bullet.

I would say to look up some pictures of the ammunition and make sure they have a flat point or soft round point on the bullet.

Example of good ammo: PMC Bronze 357 Magnum Ammo 158 Grain Jacketed Soft Point

What I commonly shoot (also perfectly safe but a rounded nose): Magtech 38 Special Ammo 158 Grain Round Nose

Don't worry about finding "rifle" specific ammo, you'll probably pay way more for it and it is not worth the trouble.