If conditionals

My mom wants me to buy her a pair of jeans online for her birthday this year. I have two options: A. Buy them online. B. Buy them in store. I want the cheapest option, so I say to my dad:

If I buy the jeans online right now, I will have to pay extra for shipping and that will be much more expensive.

VS

If I bought the jeans online right now, I would have to pay extra for shipping and that would be much more expensive.

I'm trying to save money here so should I use the first or second conditional?

Happy New Year everybody!