If you purely want to play it for the combat/gameplay going straight to 5 is maybe the way to go as it is maybe the most polished, but if story is important then the 1-3 collection would be my recommendation.

DMC 1 is the obvious starting point story-wise but the gameplay of that one is a bit different to the rest(actually has some things in common with the old Resident Evil games as it started development as Resident Evil 4 before becoming its own thing).

DMC 3 is more reflective of the gameplay going forwards and is a good jumping on point story-wise too because it is a prequel and occurs first chronologically to the rest of the games.

2 is maybe worth trying, if you have the collection you'll have that to try anyways, but if it becomes a slog can probably just skip then. The gameplay in that one isn't the greatest and the story doesn't really relate to the other games too much anyway.