I've been engaged 3 times (one of those to my DH, natch).
The first ring was an el cheapo £150 job from H Samuel (got engaged to an impoverished factory worker when I was 16).
The second was a very pretty white gold diamond solitaire.
I kept them both until I met DH and we had DD (we got married when DD was 11 months old), then I sold the first ring on ebay for £75 and the second one I pawned for £400.