If you have a -11% energy cost Wheelman, and Mastermind, this job gives 2 exp per energy point. If you have a private island (master underboss) you will get 2.125 exp per energy point. This is the most efficient job available in the game, and you unlock it at a very low level. Here is the trick to mastering all the jobs while never needing to recover energy:
1. Dump all your stamina into your "whipping boy" as soon as you level.
2. Figure out how much XP you need until your next level and how much energy you currently have (you can see EXP to next level in the "Profile" section).
3. Now, this may sound confusing at first, but here is how it works. Let's say you need 100 exp to next level and you have 75 total energy. If you do the "Bank Heist" job two times, you'll be at 59 total energy and 68 xp until next level. You can then use your remaining 58 energy to master off inefficient jobs, such as the Destroy a Mob Hideout.
3. Try to edge up close to the next level, then do the most expensive job you can afford to do before going to the next level. Once you level, any energy you leave behind is wasted, but any extra xp you earn carries into the next level. Always try to go into the next level with a head start, that way you will spend less energy doing the "Bank Heist" job before moving on to master the less efficient jobs. Here is an example:
Already 132 exp into the next level with a full energy and stamina bar
Due to some confusion, if you plan on trying this out, please read the following paragraph:
Levels 8 - 20 can be pretty slow - do not get discouraged, and do not do the Bank Heist job over and over! These will be the slowest levels that you will have following this guide. I can not emphasize this enough. Try to use the Bank Heist job as needed, if you do this too much, you'll end up behind in the long run - you need to master as many jobs as you can in order to get extra stat points for more energy. I recommend only using it twice per level, as necessary. Try not to use it before level 15. Read the comments section below for more details.
It will pick up rapidly as you master the easy jobs and get more energy. Do not dump points into Bank Heist without attempting to master other jobs. You will need the +energy you get from mastering all the jobs in order to progress. Be careful not to be frivolous with your energy spending - each time you level, the energy to exp ratio gets larger. That is, when you first start the game, for every 1 energy you have, you'll need 1 exp to level. By level 200, even if you are putting every stat point in energy along the way, it's close to 2 exp per 1 total energy. So, it is important to be efficient with your leveling along the way and master as many jobs as you can per level, but make sure you are able to get a level off of each energy bar.