There are countless wedding traditions that couples are pressured to abide by because it's the so-called proper etiquette. But there also are plenty of rule-breakers out there who say that old norms have no place in the current conversations about money and marriage.

One of the classics is how much to spend on an engagement ring. There's the outdated "three-month rule," which argues spending one-fourth of your annual salary on a ring for your fiance is the ultimate way to show your love.

But before you go spending three months' worth of your hard-earned income on a diamond, remember that this rule started as a marketing tactic created to drum up diamond sales during tough economic times, reports the wedding website, The Knot.

To put that number into perspective, the three-month rule means that someone making $50,000 per year ought to spend $12,500 on the engagement ring.

If a budget of three months' income seems like too big of a stretch for your lifestyle, you've got plenty of company. According to a 2019 survey from The Knot, the average engagement ring cost is actually somewhere around $5,900, and a good number of survey respondents (10%) said they spent less than $1,000. More recently, in a 2020 Brides' American Wedding Study, couples reported spending an average of $3,756 on an engagement ring, which is more than $2,000 less than the average 2019 price tag above.

Like everything to do with love and marriage, there's no one right answer and no right amount to spend on an engagement ring. The answer, in simple terms, is that you should spend exactly how much you can afford and want to spend.

It might be more romantic to buy a modest ring this year and use the extra cash to build a joint savings account that puts you on-track toward the shared future you want. It might sound more practical than romantic, but a shared nest egg could help you kick-start the life of your dreams, which could be more important in the long run.

But if buying an expensive engagement ring is of utmost importance, there are ways to finance it if you don't have the cash upfront. For some, making a low monthly payment is the most manageable way to go. Just make sure you can afford to make the monthly payments for the duration of your finance period.

Need help financing an engagement ring?: Using a card like the Amex EveryDay® Credit Card could help you finance an engagement ring with a 0% intro APR for 15 months from the date of account opening (after, 15.99% - 26.99% variable; see rates and fees), plus earn 10,000 Membership Rewards® points after you make $2,000 in purchases in the first six months after opening the card.

When considering low-or-no-APR financing, look into a 0% APR credit card that also has a good welcome bonus. That way, you can pay over time without accruing interest charges, while also maximizing your savings by earning cash back or rewards points to use on a honeymoon or to furnish your first home as a married couple.

If you don't qualify for a 0% APR credit card, you could sign up for a store card with your jeweler. Even though store cards come with a few hidden pitfalls, they do often offer consumers a special 0% interest period. Be sure to look out for deferred interest and/or sign-up fees if you go this route and make sure you have a clear debt repayment plan.

Not sure if you'll qualify for a 0% APR credit card?: The best 0% ARPR cards require good or excellent credit. If your credit score needs some work, look into a personal loan or consider these five ways to finance an engagement ring.

However much you decide to spend, make sure you feel comfortable with the cost. A diamond might last forever, but high-interest debt can hang around for a pretty long time.

Information about the Amex EveryDay® Credit Card has been collected independently by CNBC and has not been reviewed or provided by the issuer of the card prior to publication.

For rates and fees of the Amex EveryDay® Credit Card, click here

Editorial Note: Opinions, analyses, reviews or recommendations expressed in this article are those of the Select editorial staff’s alone, and have not been reviewed, approved or otherwise endorsed by any third party.