Depending on your budget you could select the engagement ring. About two months salary is considered the norm while deciding your budget for buying an engagement ring. Determine your budget and stick to it. Some sellers dramatically inflate prices. Never pay the sticker price unless you've shopped around and you know it's already a fair price. High-quality diamonds and diamonds one carat and larger should be accompanied by a diamond grading report. Antique rings could be certified. If no report is included, make the sale contingent upon an independent appraiser's opinion. Once you get it appraised, get your ring insured.

Engraving a message on the inside of the shank is one of the easiest ways to personalize an engagement ring or your wedding bands. The cost is usually based on the number of letters (or numbers) in the inscription, the font used, and whether it will be engraved by hand or machine.

Here are some inscriptions ideas for your engagement ring :

Forever
Always
Love is Eternal
Never to Part
or in other languages...
Deus Nos Iunxit (Latin: God Joined Us)
Semper Amemus (Latin: Let Us Love Always)
Semper Fidelis (Latin: Always Faithful)
Pari Passu (Latin: With Equal Step)
 

While deciding the ring, try the ring on. It should fit, specially since you would be wearing the ring with a wedding band. Your engagement ring should be comfortable because you may also feel like wearing the ring for other occasions too, besides your engagement. Some common styles of Antique engagement rings include the Georgian rings and Victorian rings.

Related resource:

http://www.ftc.gov/bcp/conline/pubs/products/jewelry.htm - Jewelry Buying tips