is there a maximum number of gift cards usable for a purchase

No. You can redeem as many cards as you want to your account. when you purchase something, the price is deducted from the combined total you have in your account. There are no individual cards once they have been redeemed. It's a single balance used for purchases.

See here: link-> Redeem your App Store & iTunes Gift Card - Apple Support

Limnos is correct. I was referring to the iTunes and App Store gift cards.

The number of cards for hardware purchases is limited.

Any reason you want to buy it with gift cards? Seems unnecessarily convoluted to do it that way.

If you have the cash for the cards, you have the cash for the computer.

https://www.apple.com/shop/help/payments

"You can use up to eight Apple Gift Cards at a time when you purchase online from Apple, or if you’re placing an order by calling 1‑800‑MY‑APPLE. You can use your gift card(s) with one credit card and your Apple Account Balance to pay for your purchase."

Phil0124's post was referring to an App and iTunes Store purchase. You are purchasing from the Apple Store which is different. As you can read from the above, a limit may apply under certain circumstances.

Hello lafco,

What kind of gift card?

Read this link -->

What type of gift card do I have? - Apple Support