Hi, I'll try and help you out best I can.
Shooting in RAW does take up a lot more memory, but gives you a lot more flexibility when fixing exposure and color issues. If you shoot Jpeg only and get the colors/exposure perfect, there's not much, if any, difference in terms of quality vs. shooting RAW and then converting.
No such thing as plenty of room to crop. Always do the least amount of cropping possible, as the more you crop, the more you magnify the flaws in an image. Cropping from 3800 to 3300 vs. 3800 to 2300 makes a huge difference. A general rule for my own uploads is that as a cropped image approaches 2000pix in size, the less chance there is that I'll be attempting to upload it. Anything under 2400pix means either the quality is crystal clear perfect, or I'm desperate to see the photo uploaded. This is partly because I have high standards for myself, and also because I upload at 1200pix.
No. If your aim is for upload here, never go higher than you have to. ISO100 or 200, whatever is your base, should be good enough. And I hate to dissuade you, but if it's cloudy, I stay home unless I'm really really bored. Poor light is the death of many many attempted uploads we see here.
Not sure what AL focus is. Maybe you mean AI?
Have no idea what that is, must a Canon thing. If you're shooting RAW, I doubt it matters.
I would recommend shooting in Av mode, and either getting a good photography book or at least doing some research to find out why that would be a good idea.
Good luck, and have fun!