son of a bogling

first of all, i don't use a screen recorder to capture the scene i want to gif - this usually results in loss of quality from the source material. i use handbrake to just clip the 5 or 10 seconds i need. it looks like this and in order to cut you just need to insert the timestamps.

i also make sure the exported file has the original size.

reading your message, my first thought was if you're resizing your gifs after importing the frames, because 50 mb is insanely huge.

so, after importing the frames in photoshop and cropping the gif, you need to resize it (the standard width of a gif on tumblr is 540 px). the process here is you select image -> image size -> set the width to 540 and the height to whatever value matches your desired ratio.

this is where a gif will go from over 60 mb (in my case) to less than 5.5 mb.

after doing this, you sharpen and use any other filters and colouring. of course, the size will change depending on how you edit the gif, but there's no way to make it as big as 50 mb.

another thing to watch when trying to improve the size is how many frames your gif has. i've seen in your message you said 3-second gif, but usually time doesn't tell you much, especially if you gif different media (i gif a lot of video games for example, and 3 seconds can mean different things depending if the footage was captured at 30 fps or 60 fps or more). so instead, just look at the number of frames from your gif.

i work in timeline and it shows here:

for hq footage, i try not to have more than 60 or 70 frames in a gif, because then it usually becomes bigger than 10 mb. if the difference is not big, i just delete a couple of frames to match the size limit.