Я коплю деньги на новую поездку к морю.

I am saving money for a new trip to the sea.

Breakdown of Я коплю деньги на новую поездку к морю.

• я: I
• новый: new
• деньги: the money
• на: for

Questions & Answers about Я коплю деньги на новую поездку к морю.

What is the infinitive of коплю, and what aspect does this verb have?

Коплю is the 1st person singular present form of the verb копить (to save, to accumulate).
Копить is imperfective, so я коплю деньги means you are in the process of saving money / you habitually save money.
The corresponding perfective forms for a completed result would be я скоплю деньги, я накоплю деньги – “I will (have) saved up the money (by some point).”

Does я коплю mean “I am saving (right now)” or “I save (in general)”?

It can mean both, depending on context.
Russian present tense of an imperfective verb covers both English present simple and present continuous.
So я коплю деньги can be understood as “I’m (currently) saving money” or “I (generally) save money,” and context clarifies which is intended.

Why is деньги plural? Can you say it in the singular?

In Russian, деньги (money) is almost always used in the plural form, even if in English you’d just say “money.”
There is a singular form деньга, but it’s rare and usually only in special contexts (old-style, humorous, or referring to a single coin/sum in a stylized way).
So the natural way to say “I’m saving money” is я коплю деньги, not я коплю деньгу.