A 24 carat gold band is nice but somewhat soft so you need an amalgam for the clasp and the prongs.
When I bought my wife's 1.6 carat diamond, I did some research.
I like the round brilliant.
You want your diamond well proportioned.
I'd also go for the clarity and color to be what is the minimum that collectors go for. I got a VVSI, very very slight imperfection, which is one step below flawless. If I remember right there is a big step in the cost between a VVSI and a flawless.
Next go for the color. Colors are graded in letters of the alphabet. I believe I got a color 'G' although a color 'E' is highly desired.
Go to the internet and look up the features and proportions and learn what the best proportions are for all the features such as the table, culet, crown, pavilion.
Here's a start:
https://4cs.gia.edu/en-us/diamond-c...zDDjxwcXetR1td8oSGfBuvw8swvOWryRoCXB0QAvD_BwE