Disclaimer: If you haven't read the general strats guide, please read it first.

UPGRADING PART:

Hunting for the WR recently I realized it's best to prioritize the cheapest upgrades first. The 4 top (and therefore "useful") upgrades are: Speed shot, Scorpion, Color Cloud and Fireball, more details on why the other power-ups are worse in the section at the bottom of this guide

Suggested upgrade order(for Easy):

1. Speed Shot 1(40g) - best all-round power-up, especially helpful when the line of spheres is at the very top of the screen
2. Fireball 1(50g) - why not scorpion? By the time you get enough coins to get this, purple spheres shouldn't be appearing yet, so you won't be getting any scorpions in your levels, simple, right?
3. Scorpion 1(50g) - you should have purple spheres by the time you accumulate enough coins for that
4. Speed shot 2(80g) - the least expensive, currently useful power-up, so it's an obvious choice
5. Fireball 2(100g) - following the rule of "cheapest" you can either get this or scorpion, HOWEVER, on a decent coin path, you should get be able to buy fireball 2 around 5-1 or 5-2. Stage 5 has TWO river crossing levels which can lose you a lot of time, so getting a bigger fireball
6. Scorpion 2(100g) - not much to say, cheapest available upgrade at that time 7/8. Speed Shot 3(120g)/Color Cloud(50g) - now this is the first crossroad in terms of shop purchases, on a good coin pattern, you should be able to get speed shot 3 before white spheres start appearing, and in that case you should take it first, but if for some reason you got to whites and you can't yet buy speed shot, just get a color cloud and put speed shot next. The cloud is pretty big anyways.
7. Color Cloud 2(100g) - the only exception to the cheapest rule because SS3 before is more expensive than this
8. Scorpion 3(200g) - it's better in lategame than fireball
9. ... - you will probably buy the 3rd scorpion upgrade late into stage 10, or in early 11, so it's possible you won't be able to afford anything (and getting an upgrade on 11-4 won't save you any time probably) even if it's just 40g, but if you are in stage 11 BEFORE the river crossing level, get yourself a Reverse 1 (40g) While in normal levels Reverse is rather useless or even negative, in River Crossing it's very powerful because it's able to clear the entire river for a while, so I decided to upgrade it to make it better.

RNG MANIPULATION PART:

Upgrade colors(number of pluses indicates how good a certain color tier is): Red+++ - Speed Shot, Fireball Green - Reverse, Net Blue+ - Lightning Bolt, Slow Yellow+ - Wild Ball, Stop Purple++ - Scorpion, Color Bomb White++ - Color Cloud, Color Swap Black - Match Highlighter, Pyramid Blocker Cyan+++ - Color Sorter (insanely strong power-up, not relevant on Easy though) Orange+ - Sandstorm (More explaination on "why is that tier so good" in the "proper use" section below)

Ideally, you want to force the drop of power-ups that you're upgrading (the top4) so just prioritize these colors as the third combo shot if you can. If I get a red sphere, I usually "store" it (by swapping to whatever other sphere I have) and try to get a combo x2 with anything else I get; that way, I'm guaranteed to be able to get a red power-up if the other 2 spheres have a match on the board.

PROPER USE OF POWER UPS (Tier 4 is best, unlike regular tierlists, don't @ me) Tier 0 Net - Don't [actually, Net is the WORST power-up in the game because with it you will catch everything, so you can't skip a falling stop or reverse which will lose you time] Match Highlighter - bother [doesn't do anything if you're even semi-decent at the game] Pyramid Blocker - catching [useless, might help you in] Stop - them. [on some levels it can be ok, on some it can block you completely for 2 seconds, either way it loses time] Tier 1 Reverse - usually it's garbage, but if caught during the roll-out (when a new line of spheres enters the level it's always at a much bigger speed) it can help you aim, and reverse is kinda OP in River Crossings. These 2 things however aren't enough to make it worth it. Slow - it's eh, will slow you down but helps aiming, can also be very helpful during the roll-out but Wild Ball - it's ok, but not much more. Use it to clear singled out spheres, clearing two nearby single spheres with a wild ball saved you 3 shots. Apparently if you shoot a wild ball between red and yellow as the 3rd combo you can get the orange power-up, happened to me but I'm still not 100% sure. Lightning Bolt - also ok, try to aim for single spheres on horizontal-only levels, you can take out two if you aim it properly. On levels with vertical paths, shoot at the vertical segment when it's "full" (it's often even worth to wait). The weird spiral on 5-1 is a great example of a spot to use lightning on Tier 2 Fireball/Color Cloud - Same idea with both, try to aim either for big groups of different colored spheres or into spots where you can hit the biggest amount of spheres (sharp corners, crossings, insides of bends) Color Swap/Color Bomb - Bomb is a bit better, but both effectively eliminate a single colour from a train. With the swap, the best target are spheres that are next to the color you're swapping to Tier 3 Scorpion/Speed Shot - these two don't need explainations, just get them as much as possible Tier 4 Color sort - holy macaroni is this one OP. On easy you can only have it in certain survival levels, and you should use it to farm some extra Ankhs, but in other difficulty levels prioritize it over anything else. It doesn't need any upgrades and it makes you clear levels FAAAAAST