Learn Hardcore Russian: Давайте купим ещё одну пару джинсов.

“давайте” plus the first-person plural future form (here купим) is the standard Russian way to say “let’s.” It’s not a request directed at someone else; it’s an inclusive suggestion involving the speaker and the listener(s).

Why is купим in the first-person plural (we will buy) and not an imperative?

Because after давайте you always use the first-person plural form of the verb to make a collective suggestion. If you wanted to command one person, you would use the second-person singular imperative: Купи ещё одну пару джинсов (“Buy another pair of jeans!”), which is more of an order than a suggestion.

Why do we say еще одну instead of just еще or одну?

еще means “another” or “one more”
одну is the accusative feminine form of “one” (because пара is feminine)
Combining them (еще одну) gives “one more (feminine item),” i.e. “another one.” You could drop одну and say купим ещё пару джинсов, but adding одну stresses that you literally want one additional pair.

Why is пара in the accusative case?

пара is the direct object of купим (we are buying it), so it takes the accusative. Since пара is an inanimate feminine noun, its accusative form looks like its nominative: пара → пару.

Why is джинсов in the genitive plural and not джинсы?

When you use пара (pair) to quantify something, the word for the thing moves into the genitive plural:

nominative plural: джинсы (“jeans”)
genitive plural: джинсов
Thus “a pair of jeans” → пара джинсов.

Why is it одну and not один or одно?

Russian adjectives and numerals agree in gender with the noun they modify. Пара is feminine, so “one pair” uses the feminine accusative одну.

masculine: один
feminine: одна → accusative одну
neuter: одно

Could I say давайте купим ещё одни джинсы instead?

Yes. еще одни джинсы literally means “another pair of jeans” without using пара. Note that одни is the only form of “one” used with plural‐only nouns like джинсы. But using пара is more explicit if you want to emphasize “one more pair.”

I’ve seen еще written as ещё with dots over the “e.” Which is correct, and how do you pronounce it?

The correct letter is ё (pronounced “yo”), so ещё is the proper spelling.
In many texts, publishers omit the two dots and write еще, but you still pronounce it [йо].
Stress always falls on -щё: [исˈчо].