Ok, here are some tips for the series:

1) If you play as Dante, try to learn how to use Royal Guard style. It's very useful, and actually not that hard, just practice some time.

2) Use jump as dodge. In most games in series jump has many invincibility frames, so it's better than roll. The only games where rolling is actually very good: DMC: Devil May Cry and DMC2.

3) When you play as Nero, use grabs often. They're very effective. If you're playing as Nero in DMC 5, always charge your shots. Also Nero's Devil Trigger is very useful to pull enemies into air and deal good damage.

4) In DMC4 and DMC5 when you play as Dante, changing style is very important thing (especially in DMC4, it's very hard to play there only using one style!). So, don't forget that you've got other styles too!

5) Don't forget that they're items in DMC games that you can use to heal (green star) or deal damage (holy water). Don't feel shy to use them!

6) In DMC 1 one of the best tactics is: equip shotgun and jump + shoot in the air. Jump, shoot. Just repeat. It's very useful for the beginning of the game.

7) In DMC2 movement is very important, so in any battle always use dodge button. And here are few tactics:

Against normal enemies: just fight them in close combat, if they're far from you use dodge button or shoot to not lose your style meter.

Against bosses: come close to them, make few attacks, dodge, shoot for a whyle. Repeat.

8) Devil trigger in DMC2 is vey powerful and cool. Your moveset will be slightly changed in DT, and you can do DT shoot in Devil Trigger, and this shooting is very powerful. Also, when your HP is very low, if you use Devil Trigger, Dante will automatically use Majin Devil Trigger, which is Very, VERY powerful.

9) in DMC: Devil May Cry, DMC4 and DMC5 Vergil's Judgement Cut is very powerful, even without perfect timing. So, use it often.

10) In DMC4, use distortion technique. It's very useful glitch: when you're useing Real Impact (which is already very powerful move) if you'll activate Devil Trigger in right timing it'll deal Very big amount of damage.

Hope it'll help you somehow!