Έχω ένα μικρό όνειρο για το μέλλον μου.

In everyday Greek, Έχω μικρό όνειρο sounds incomplete or unnatural; you almost always use the article here.

• Έχω ένα μικρό όνειρο = I have a small dream.
  This is the normal, natural phrasing.

You could drop ένα only in some poetic or very stylised language, or if μικρό όνειρο was already clearly defined from earlier context, but that’s unusual. So for standard speech/writing, keep ένα.

The neutral, most common position for an adjective in Greek is:

article – adjective – noun
(ένα μικρό όνειρο)

Here:

• ένα (article)
• μικρό (adjective)
• όνειρο (noun)

All three agree in gender, number, and case (neuter, singular, accusative).

Other orders are possible but change emphasis:

• μικρό όνειρο (no article) – tends to sound like a generic description, less natural here.
• ένα όνειρο μικρό – possible in more literary/poetic styles, placing extra emphasis on small as a kind of afterthought.

In Greek, adjectives and articles must agree with the noun in gender, number, and case.

• όνειρο ends in -ο, which is a common neuter ending (especially in nominative/accusative singular).
• In dictionaries you’ll see το όνειρο – the article το also tells you it’s neuter.

So:

• Noun: όνειρο – neuter, singular
• Article: ένα – neuter, singular, accusative (because it’s the direct object of έχω)
• Adjective: μικρό – neuter, singular, accusative to match όνειρο

They all line up with each other.

για is a very flexible preposition, often translated as:

• for (purpose, benefit)
• about / regarding (topic)

In για το μέλλον μου, the sense is closer to about / regarding my future, but in English we naturally say for my future in this kind of sentence.

So you can think of it as:

• όνειρο για το μέλλον μου ≈ a dream about my future / a dream for my future.

Grammatically, για normally takes the accusative: το μέλλον μου is in the accusative case.

Modern Greek prefers prepositions plus the accusative for this kind of meaning:

• για το μέλλον μου – preposition για
  • accusative; very natural, everyday Greek.

Forms like του μέλλοντός μου (genitive) are:

• more formal or old-fashioned,
• more typical of written, literary, or very formal contexts,
• and usually used in slightly different structures.

So:

• όνειρο για το μέλλον μου – normal, modern, spoken style.
• όνειρο του μέλλοντός μου – possible, but feels very formal or literary.

In Greek, weak possessive pronouns (my/your/his…) usually go after the noun:

• το μέλλον μου – my future
• το σπίτι σου – your house
• η ζωή του – his life

So the pattern is:

article – noun – possessive pronoun

Not like English, where my comes first. Saying something like μου το μέλλον would be unusual and would need a special emphatic structure; it’s not the normal way to say my future.

Yes, Greek word order is quite flexible, and both are grammatically correct:

• Έχω ένα μικρό όνειρο για το μέλλον μου.
  Neutral, default order.

• Για το μέλλον μου έχω ένα μικρό όνειρο.
  Slight emphasis on για το μέλλον μου – like As for my future, I have a small dream.

The second version can sound slightly more expressive or rhetorical, but it’s still natural.

όνειρο covers both meanings:

1. Dream during sleep:

   • Είδα ένα περίεργο όνειρο. – I had a strange dream (while sleeping).

2. Dream/hope/ambition:

   • Έχω ένα όνειρο να γίνω γιατρός. – I have a dream to become a doctor.

In your sentence Έχω ένα μικρό όνειρο για το μέλλον μου, the phrase για το μέλλον μου strongly points to the ambition/hope meaning, not a sleep dream.

In Greek:

• μικρός / μικρή / μικρό = small, little in size, amount, importance, intensity, etc.

  • μικρό όνειρο = a small / modest dream.

• λίγος / λίγη / λίγο = few, little in the sense of quantity (not much / not many).
  You use λίγος mainly with uncountable nouns or to say a few:

  • λίγο νερό – a little water
  • λίγα όνειρα – few dreams

So:

• μικρό όνειρο is correct and natural.
• λίγο όνειρο is not normal Greek.

Stressed syllables are in capitals here:

• Έχω – É-cho (É-ho)
• ένα – É-na
• μικρό – mi-KRÓ
• όνειρο – Ó-ni-ro
• για – ya
• το – to (like toh)
• μέλλον – MÉ-lon
• μου – mu (like moo)

Put together (roughly, in Latin letters):

É-ho É-na mi-KRÓ Ó-ni-ro ya to MÉ-lon mu

Each word keeps its own stress; Greek is not strongly reduced like English, so all vowels are clearly pronounced.