Defiance Free to Play

This achievement requires you to put an EGO unit into fifty skills.

You could naturally earn this by reaching a very high level and tactically placing your skill points but that would take an inordinate amount of time and would probably leave you with a pretty poor class setup.

However, there is a much faster method, providing you have around 10,000 spare Scrip.
When you are in the EGO perks screen (Press start and then RB twice) you can press Y to Respec. This gives you back all of the Ego units you have spent for a small fee (For me it was around 3000, but it depends on your level) This allows you to replace those skill points all over again and you still earn credit towards this achievement.

It may take a few Respecs, depending on your level, but it can be done at any point in the game. Sometimes you need to submit the Respec using A once you have placed the points, make sure to do this otherwise it won't save and you'll have to do it again.

One final thing to keep in mind; there's also an achievement for leveling a perk to max 25 times, so you could potentially work on getting that one at the same time. Also, the achievements involving completing Pursuits - many pursuits involve using the four different action skills so it might save some time and scrip if you were to choose a different starting skill each time and play for a short while to help your progress before Respeccing again.

If anyone finds any other useful tips, errors or shortcuts feel free to leave a comment and I'll update and add credit. Cheers guys!