Start with 'The Secret of Monkey Island'. £2.37 on Steam [0]. I spent hours on my Atari ST wondering how to get past the governor's dogs. With no WWW to look for cheats I ended up asking at my local independent computer shop (remember those), and one of the guys told me how to do it.
[0]http://store.steampowered.com/app/32360/The_Secret_of_Monkey...