Bayaran muna ang mga bayarin, saka gumastos.

They come from the same root, bayad, which has to do with paying.

• Bayaran is the verb here: Pay
• Bayarin is a noun here: bills, dues, or things that need to be paid

So in this sentence:

• Bayaran = pay
• ang mga bayarin = the bills

Even though they look very similar, they are doing different jobs in the sentence.

Both are possible, but they use different verb focus patterns.

• Bayaran ang mga bayarin uses an object-focus pattern. It highlights the thing being paid.
• Magbayad ng mga bayarin uses an actor-focus pattern. It highlights the action of paying more generally.

So:

• Bayaran ang mga bayarin = Pay the bills
• Magbayad ng mga bayarin = Pay some bills / do the paying of bills

In many everyday situations, both are natural. The given sentence sounds very direct and fits the idea of take care of the bills first.

In this sentence, ang marks the noun phrase that the verb is focused on.

Because bayaran is an object-focus form, the thing being acted on is marked by ang:

• Bayaran ang mga bayarin

This does not simply work like English the. Filipino ang is a grammatical marker, not just a definite article. In this sentence, it shows that the bills are the main target of the action.

Mga is the plural marker.

• bayarin = a bill / a due / something payable
• mga bayarin = bills / dues

So ang mga bayarin means the bills.

Muna means something like:

• first
• for now
• before anything else

In this sentence, muna tells you the order:

• Bayaran muna ang mga bayarin = Pay the bills first

It often adds the sense of do this before moving on to the next thing.

Saka means then, after that, or afterwards.

So:

• Bayaran muna ang mga bayarin, saka gumastos.
• Pay the bills first, then spend.

It links the two actions in sequence:

1. Pay the bills
2. Spend after that

They are related, but not always identical in use.

• saka often means then / afterwards
• at saka can mean and then, and in some contexts also and also / besides

In your sentence, plain saka works well because it is mainly showing sequence:

• first this, then that

Gumastos is used because the sentence is talking about spending in general, not about a specific thing being spent.

• gumastos = to spend
• gastusin = to spend something specific / to use up something

Compare:

• saka gumastos = then spend
• gastusin ang pera = spend the money

Since no direct object is stated after gumastos, the actor-focus form is the natural choice.

Yes, but that is normal in Filipino commands.

The sentence is understood as being directed at you, even though no pronoun is stated. Filipino often leaves out pronouns when they are obvious from context.

So this sentence naturally means:

• Pay the bills first, then spend.

If you want to make you explicit, you could say:

• Bayaran mo muna ang mga bayarin, saka ka gumastos.

That makes the addressee more visible, but the shorter version is also fine.

Functionally, it is an imperative: it gives an instruction or advice.

• Bayaran here is clearly command-like: Pay
• gumastos after saka also has an understood command sense: then spend

Filipino often uses bare verb forms in this kind of sequence, especially in short instructions.

Not always.

As a noun, bayarin often means:

• bills
• dues
• payables
• something that needs to be paid

But depending on context, a form like bayarin can also be analyzed as a verb form from bayad. In your sentence, though, it is clearly a noun because it appears in:

• ang mga bayarin

The plural marker mga makes that very clear.

It is natural enough, but yes, learners notice the repetition right away because both words come from bayad.

That kind of repetition can happen in Filipino because related verb and noun forms are often built from the same root. Native speakers generally understand it without any problem.

A slightly different but equally natural version would be:

• Magbayad muna ng mga bayarin, saka gumastos.

But the original sentence is still grammatically fine and understandable.

You can add pronouns or particles, depending on the tone you want.

Some natural alternatives are:

• Bayaran mo muna ang mga bayarin, saka ka gumastos.
• Magbayad ka muna ng mga bayarin bago gumastos.
• Bayaran mo muna ang mga bayarin bago ka gumastos.

These can sound more personal and conversational than the very short command style of the original.