If you guys like it, I can add audio commentaries, even if my english accent isn't that good :( I can comment in french as well.
What I can say here:
If you want to try my strategy, follow my gaz vespene purchase order, as well as my mineral expenses.
I will explain few stuff:
You play with Blasting towers because they deal damages to several enemies at the same time.
Blood Towers are bad. Of course u can win normal with blood towers, if u want I can win normal doing any tower of ur choice without a leak... that's pretty damn easy, so don't use normal as a reference. That tower is weak because it is very slow and only touches 1 target, you get 1 up for the bosses (mothership, battlecruiser) and to deal with invisible guys if they seem to go too far, because that tower can move (mobile tower is really bad).
Electron towers (protoss canons) only have one useful feature: their stun. Unfortunately if you rely on it to win, you won't go far. I only build them early to win all the bonuses, increase my crowd appeal early and use the stun later on through tanks (auxiliary), which is the best tower in the game, by far.
The goal of the game is to win of course, but the best way to win is NOT to build blood towers everywhere... The best way to win is to make money, so it is to increase your crowd appeal and your admission, so maximize your kills with the tanks and the various kill bonuses.
If you don't understand why I do a supply first, and then the research for support tower when I only use few of them, here is the reason:
The extra concussion canon I use at the begining slow down the ennemies, it helps to avoid any leak. Then as a party canon you get more money. THe reason the purchase the upgrade to make those 2 bigger is the crowd appeal they bring (= more spectators), for 5 mineral, you get 20 more people every day, which is a game changer at the beginning.
Luck factor is unfortunately something you can't control... the earlier you have your mineral the better, I do the kill research for homing missile to try to increase my luck, but you never know.
You need the tanks (auxiliary tower) before wave 14.
If your crossfire/chaosfire tower reaches 100/100 and u don't have any spectacular kill, change the tank focuses for anything else, crowd appeal with burnout, or more mineral with homing missiles.
I do 1 chaosfire for the following reasons: it deals a lot of damage to a single target, benefits from Master Blaster upgrade like the rest of your towers, has the same kill bonus as the crossfire so you can focus a tank on it, and it is way cheaper than the painter, which I used before.
Painters can be used with this strategy instead of the front tanks, but you will have leaks.
I start building towers that may seem "random" at some point (corruption, splitting, mobile etc) because of the Park Planner upgrade. That upgrade improves the number of spectators based on the TYPE of tower you have at 3, 4 and 5. There are 12 types of towers in the game, the sooner you have all 12 at 5 the better. In lower difficulties, you can achieve that way earlier because the ennemies are really bad, 3% and lower difficulties are way too easy with this strategy ;).
Killing my own Lester is the secret alternative ending of the game, it doubles the buy out, so you gotta do it.
This is not the strategy I used for my current highscore, but this one is safer. In my highscore I add tons of leak, but a bigger crowd appeal (and got more lucky with the mineral), so my park was worth way more.
My best spectator count was 22k at the end in 3%, 20k in 4% for my highscore. I heard of strategy with 30k + spec, but I heard it was based on spamming the map with low level towers to increase the crowd appeal, which has been fixed now, with spectators losing interest in them at some point / getting bored if you do too many of the same tower.
If you have questions or request let me know, I still play the game everyday and would be happy to help out / play with you, and of course improve my strategy!