@MercWithMouth - unless you are paying to buy dark crystals, by far the best tower to get first is the Sniper tower, then unlock the 20% KO x3-5 damage ability before you do anything else. None of the other towers come close to touching it, except in situational levels.
@Zaptue - coming from the guy that very obviously pays to play the game, that doesn't mean much. If you PAY to unlock everything, sure, some things can be occasionally useful. Although if you've unlocked and upgraded the amount that I can see you have, and are STILL only 2/3 done with the last map, you quite frankly aren't good enough at the game to be giving advice.
Most of us aren't interesting in investing money in this shallow game, we just want to get to level 35 and never play it again. Right now I'm on track to unlock MAYBE two abilities by level 35. Ergo, it is far more efficient to focus your tower upgrades on that single tower that is useful 95% of the time, not start unlocking towers that might possibly be useful 5% of the time.
Normal people take 5 dark crystals to get a single ability. Barring special events, you get a single dark crystal every 3 days. So a normal person gets a SINGLE ability once every two weeks. You buy an ability, you have to wait 2 weeks to get your next one. So given that there are 24 abilities total, I seriously doubt anybody is interested in waiting 48 weeks - basically a full YEAR - to unlock the last few crappy abilities.
For the large number of people that refuse to pay money for this shallow game, upgrading and building a single tower is FAR more efficient for progressing.
And even if you are willing to pay to upgrade everything, there are still just a couple towers that are VERY OBVIOUSLY far better than anything else, some of them are just trash.
Let's take a second and objectively compare a few towers. First let's look at Jungle Warfare versus Sniper Lookout, and the first levels of their abilities.
Base damage for a Jungle Warfare tower is 365-600 and attack speed 0.5. That gives you an average DPS of 965. Base damage for a Sniper Tower is 830-1500 with an attack speed of 1.2, average DPS 970.83. So they have essentially the same damage... but Sniper Tower has SIGNIFICANTLY higher range. So Sniper Tower wins out easily on just base stats.
Jungle Warfare's first ability is.... +15 range. Which still leaves it at less range than a Sniper Tower. So now you are looking at a MORE EXPENSIVE tower, with LESS damage and range than the Sniper Tower.
They both have a damage increasing ability. Except.... the Jungle Warfare upgrade is so small that it is laughable. At tower level 28 and kingdom level 29, it adds a paltry 30 damage per shot. That's not even NOTICEABLE until you have 10+ shots on a single target, and even then it's still only tiny upgrade. Let's be incredibly charitable and say you average 20x shots on a target. that gives an average of +150 damage per shot for every shot. Again, at tower level 28, which has an average damage of 2907 a shot, that equates to... barely a 5% damage increase. And oh, by the way, since it is a FLAT amount, it gets WORSE as levels increase. Even the max level of the ability (80 per shot instead of 30), still only equates to a 13% damage increase at tower level 28, 6.5% at tower level 56. And again, that's with my incredibly charitable 20x shots per targets calculation.
That is compared to the Sniper Tower 20% chance for a KO or 3-5x (an average of 4x) damage. Disregarding the KO chance, which would have to be calculated based on average mob health, a 20% chance for 4x damage equates to an 80% damage increase on the tower!!! Add in the KO chance and you are looking at an average of an OVER 100% damage increase from a single upgrade. And the best part? Since it is a % increase, rather than a flat amount, IT STAYS THE SAME AS YOU LEVEL TOWERS. And it only gets higher as you level the ability. The level 3 ability (60% chance for 7-9x damage), equates to an incredible 480% damage increase for the tower (though admittedly you will have to factor in overkill when you start hitting that hard, but who cares, they 1 shot a mob).
I could keep comparing the exact numbers for towers, but I'm getting a little bored, and the point is made.
Before you factor in the 1 hit KO chance, Sniper Tower absolutely blows Jungle Warfare (and anything else) out of the water. Conclusion? There is literally no reason to EVER buy upgrades for, or build a Jungle Warfare tower, or pretty much any other tower, while Sniper Towers exist.
The Wizard Tower abilities essentially boil down to sacrificing a significant amount of damage in return for a CC ability. Which still isn't particularly useful unless you have the damage to back it up, relegating them to a 'build one or two a level, MAYBE'.
All of the 'Summon Elemental' skills are almost totally useless. Just like Warriors, they do a laughable amount of damage and with their still rather low health, still get torn apart by any mobs you'd actually have trouble with, leaving them as a tiny speed bump. And given the lower amount of damage the tower is already doing, the speed bump isn't even as useful as if you'd just built a damage tower in the first place.
Cannon towers have much lower damage, and because the game doesn't let you target specific mobs, more often than not they just hit ONLY the guys at the front, leaving them hitting just a couple guys at a time.
Dragooner's are actually decent, and I do build a couple occasionally, but again, their power is only useful when they hit multiple mobs with every shot. Their 'explode' ability suffers from the Flat Damage curse, and with the developers obsession with balancing everything through piling on more HP, it becomes rapidly useless.
The point is that because Sniper Tower's ability actually scales with tower upgrades, and at a huge rate at that, it makes it hideously more efficient than literally any other tower. Given that it is better, why would you waste time, money and upgrades on less efficient towers?
Other than a couple gimmick levels, you are far better off just building Sniper Towers.
And that's a knock on the developers. Since they obsess with essentially balance everything by increasing HP rather than ACTUALLY putting effort into it, the scaling tower is king. Flat damage becomes rapidly useless, and CC is only useful if you have the damage to back it up - most of the time you're just better off piling on the damage.