Millennials may have the most successful romantic relationships if money could buy love. Those aged 35 to 44 plan to spend the most on Valentine's Day, an average of $336, according to a survey.

They are followed by consumers aged 25 to 34, who intend to spend $238 on average. Both groups are much higher than the $193 national average for people who will spend money on Valentine's Day.

According to the National Retail Federation's annual study, Americans plan to spend $25.9 billion on Valentine's Day this year. This is an increase from $23.9 billion the previous year, and it is the second-highest year for spending since NRF began tracking in 2004.

According to the survey, just over half of participants intend to celebrate Valentine's Day, albeit not all of them will spend money doing so. But if you want to express your love with a gift or an event, Pattie Ehsaei, a financial consultant, told CNBC Make It, "never go into debt for love."

Ehsaei offers guidance on money, careers, and social etiquette using her more than 20 years of experience in legal and financial services. She cites this as the "No. 1 financial rule for relationships": don't go into debt out of love.

Much has changed over the years, but classics like chocolate remain to be in style, with sweets, greeting cards, and flowers topping the list of things shoppers will buy for the holiday.

Some customers may be purchasing items other than chocolate and flowers. According to wedding planning website Wedding Wire, Valentine's Day was the most popular day to get engaged in 2020.

When it comes to shopping for an engagement ring, though, you should definitely plan ahead. According to The Knot 2021 Jewelry and Engagement Study, the typical engagement ring costs $6,000 in 2021.

Before someone pops the question, Ehsaei advises couples who are thinking about getting engaged to talk openly about their finances.

And Ehsaei advises finding less expensive options if money is short.

She advises against purchasing a genuine diamond engagement ring and suggests lab-grown diamonds or moissanite as more affordable options that will nonetheless dazzle your significant other.

"That money can be utilized for so many other things, like a down payment for a home, paying off debt or savings."

"You don't have to spend a lot of money to be romantic," Ehsaei advises when it comes to buying for your significant other. If you want to exchange gifts with your partner, she suggests coming up with a budget together.