FX setting is the one that controls the Gore Detail Settings (amount of Blood, Gore, Particles and Corpse Amount) If you think youre struggling because of the Gore settings try to set FX Quality Setting to Low in the Game Menu and Test if your Framerate is considerably better. It features a unique 'Drag-and-Drop' system which allows non-programmers to make simple games. Additionally, experienced coders can take advantage of its built in scripting language, 'GML' to design and create fully-featured, professional grade games.
For my blood texture, I really just googled an image, found one that looked alright, I could modify it to make it look a bit better, but it does the trick. Like ReBirth mentioned, if you want it to be more accurate, you want to make it go in the right direction, mine is just random, starts from the player, and gets pushed out, It doesn't move for very long, and makes it look like its been pushed out a little. To increase performance, you could check to make sure the blood is within the players view before rendering it, you could make the image fade away / disappear after a certain time, or after the player moves away from its view. My game is pretty much the same concept as yours, so if you look how I do it, you may get a idea to improve it. Yeah, I tried that, but it lagged the game sooooo much.
Went from 60 to 25. How would I make them efficient? Perhaps your original idea was actually correct, but maybe there was something causing that lag? I recently added death effect to my game and had about 200 or so particles go into the physics box2d and at first it lagged hard. It wasn't until I realized that I was checking some collisionLists and was checking the particles against a bunch of things they shouldnt be. Especially in box2D with 'getFixtureA' being called (thousands of times) lagged my game out hard.
When I filtered out the particles, the game never even flinched, even at 100x the amount of particles. How were you handling it that caused the lag? Unless you are aiming at a very low end system(mobile), a few hundred, or even a few thousand particles shouldn't be much of a problem at all. However when dealing with many particles, its easy to overlook an expensive method call. Edit: Also your current blood doesn't look so bad, I would make the blood pieces much smaller, possibly circular, and have many more of them.
Perhaps 1/10th the size and 10x the amount, so overall its about same, but itd look much more like splatter.