Tiny Guide to Levelling Generals
I. Identify your build:
If you already don't have an idea as to what your build should be good at, follow these rough guidelines. If you only do pvp (and guild battles) you will have a high bsi and a low lsi. If you only do monster hunting and pvp by necessity only (eschewing guild battles) you will have a high lsi and a low bsi. If you do pvp/gb and monster hunting you will be somewhere in between with less of a drastic difference in your bsi and lsi and you are a hybrid.
II. Narrow your focus to 1 primary general and 1-2 secondary generals:
Spreading out your scarce hero crystals is generally not a good idea because you will want to level 1 general as high as you can as quickly as you can since the general's stats are very important in both pvp and monster hunting, and the ability of the general scales with his level. A level 80 Barbarus or a level 80 Sahar is in all cases better than a level 64 Maalvus AND a level 64 Sahar because of the extra 150 att/def of an 80 over a 64 which will benefit in better pvp strength and in increased damage on all monsters and because the added bonus to the primary ability of Barbarus or Sahar is even more increased damage to monsters. Knowing that you will be focussing on only one general makes your choice of your primary general easier, as you can compare level 80 abilities to make your choice rather than dithering between one general and another. If you are a free-to-play dinosaur build for example, you can choose a general like Sephora for the +42 max stam/ene at level 80, as her primary ability fills in the deficiencies of lsi for your build.
III. Know your crystal investments and plan accordingly:
The wiki is a good source of information. http://castleage.wikia.com/wiki/Hero_Crystal shows you all the information you will need for this step. No matter what you decide, you can add up all the crystals you will need for your general and plan accordingly. For a free to play style I fully recommend choosing the balanced type of general because blue crystals are by far the easiest to gather since natural token regeneration of 1 per hour is much faster than 150 stamina regeneration or 300 energy regeneration, which are the resources needed to get a chance at a blue crystal drop, a red or green crystal drop, or a green crystal drop.
You will need blue crystals. You will need red crystals. You will need green crystals. These types drop only on certain days, so to farm reds or greens plan your heaviest monster hunting on those days. To farm blues, join a high level guild to increase your chances on blue crystal days, and spend as many tokens as you can in that time period on land of earth. A trick to spending stamina is to join a slowkill monster, on non-crystal days hit that monster only with 200/600/1000 stamina attacks, then on the first crystal day (friday for green and sunday for red) hit the monster with 10 stamina attacks until the backlog of stamina to essence drops is cleared (until you stop getting essence drops for those 10 stamina hits). A trick for blue crystals is to save up to your token limit on monday and dump them all as soon as you hit midnight pacific standard time (when blue crystal days start).
V. Level up your secondaries when your crystal farming allows:
If you gather more hero crystals than your colored crystals rate demands (you need 108 red crystals and 40 hero crystals, but you already have 40 hero crystals and you need dozens more of the red) feel free to spend those extra hero crystals on your secondary generals. Otherwise, stick to your plan, and truly keep your primary general the primary focus of your efforts. Similarly, if you gather more colored crystals than hero crystals, consider doing the alchemy for hero crystals or guild coins.
That's about it, taking these steps will give you a clear timetable as to what you can accomplish in a given time period, and seeing the end of your efforts is halfway to completing your goal. Good luck, good loot, and have fun!