I can't say from a technical standpoint but "in theory" holding to about 20MB or less would be good. Consider how long 20mb takes to download in a browser on a variety of broadband, from DSL (1.5 speeds) which would take about 2:35 (thats 2 min 35 sec) to low level cable internet at 10Mb/sec ( 24 sec) vs high end broadband where it'll take 4-7 seconds. Then consider those using their smart phone and trying to view it on a data plan or on a less than ideal connection.
I found this handy calculator that may help you decide:
http://www.numion.com/calculators/time.html
If compressing animated gif's is an issue, have you considered cropping them much tighter to show only what you intend to highlight for a specific image? I'm not sure if you're calculating based on "whole screen" capture or a vignette.
I'm not crazy about TONS of animated gifs personally, it gets very busy after a while and unless the examples are starkly different they tend to run together and my eye glazes over them.
Are you limiting the palette at all? possibly do a 256 greyscale with dithering? if the game is going to be a black white and grey affair it might be worth stripping the color coding off to cut down on overall image size.