3 Things I Always Buy at Costco

Costco has become the cornerstone of our grocery budget and a major help to our personal finance goals. In fact, according to our Mint budget, we've been saving about $200 a month since we started shopping there more frequently.

Granted, we live in the Pearl District of Portland, Oregon, and some of those savings are likely because we're driving out of town. Shopping at Costco also means we now avoid a former drain on our budget -- Whole Foods. Even so, there's no denying the warehouse is saving us money on items we use frequently. I could name dozens, but if I had to pick three, the following products we would buy nowhere else.

1. Diapers

Recently, my wife and I had our first baby and quickly discovered why it costs about $300,000 to raise a child from birth to age 17.

Costco, however, has really come in handy, especially for diapers. For a box of 192 Kirkland Signature Diapers, you'll pay $34.99, which comes out to about $0.18 a piece. Even if you opted for the more expensive Huggies, Costco would still give you a very competitive price. For perspective, here's how it stacks up against some competitors.

Costco also has great deals on other baby necessities, like wipes, baby monitors, and cribs.

2. Olive oil

Our household uses a lot of olive oil. Everything has to be sott'olio, as my grandparents would say, which basically means submerged in a pool of oil. As frugal as we are, this is one product whose quality we can't sacrifice to save a buck, even though olive oil prices have surged with inflation.

Costco's olive oil isn't the cheapest on the market, but the price is really good for this level of quality. For a 2-liter bottle of Kirkland Signature 100% Italian Extra Virgin Olive Oil, you'll pay about $17.99 in-store (or $18.99 online). That's a price we're willing to pay, especially after tasting the olive oil and realizing it's not a cheap generic brand.

If you're not a stickler for olive oil, you could save even more by buying two 3-liter jugs for $49.99, which comes out to about $8.33 a liter. That's pretty competitive with other stores. For example, Walmart sells 3-liter jugs for $25.87 and Amazon sells half a liter for $5.99.

3. Gift cards

Lately, I've gotten in the habit of checking prices for Costco's gift cards online before I buy from another retailer. Why? Because buying gift cards from Costco means getting about 10% to 30% of your gift card's total value for free.

Costco typically rotates its gift card selection, but you'll often find restaurants, airlines, gaming companies, movie theaters, and other retailers. Two gift cards that have really caught my attention recently are from Southwest and Alaska Airlines. When you pay $449.99 for gift cards from either airline, Costco will give you another $50 to make it $500 in total value. Since my parents live in Georgia -- and are eager to come see their granddaughter -- we've been looking at these gift cards as a way to fly them out more frequently.

How to find more good deals at Costco

One of the best ways to stay on top of good deals is to download the Costco shopping app. You can enable Costco to notify when it posts new products and deals. The app doesn't have the strongest features -- it won't let you scan-and-go like other stores -- but it can at least make navigating Costco's unruly website a bit more manageable.

All said, Costco's low prices on baby supplies and essential foods have really helped us save money this year. Like other members, I'm grateful Costco can help me rack up less on my credit card without forcing me onto the ol' beans-and-rice diet. Take a look at these products next time you're at the warehouse and see if they can find a place in your lineup of favorites.