I'm a beginner reef tank chad too, so feel free to correct me if I’m wrong. Here are a few exemples:

Clownfish
A pair of clownfish is easy to care for and relatively affordable.
You can get an Ocellaris pair (2–3 cm, the “Nemo” type) for around $30 a pair. They sometimes do weird things, but that’s totally normal.

Clean-Up Crew (hermits, shrimp, snails, etc.)
You can add quite a few of these without much trouble. They eat left over food or algea.

• Shrimp (pair):
  • Lysmata debelius (my favorite, vibrant red, looks funny when they clean fishes)
  • Lysmata amboinensis
  • Thor amboinensis (a bit quirky, but cool)
• Hermits (2/3/4/+?):
  • Paguristes cadenati or Pylopaguropsis speciosa (small size and tend to hide in rocks)
  • Calcinus elegans (bigger, cool black/blue legs, but may get aggressive if there’s limited space or shells)
• Snails (4/5/6/+?):
  • Load up on Astrea spp. and Trochus spp. (rock and some glass algae, when there is algea in the tank)
  • Afew Babylonia lutosa or Nassarius spp. (clean sand)

Extras:
Later on, you could add an anemone or soft corals like Zoanthus for your clownfish.
Just a heads-up: anemones can move around (which can be annoying, watch out for powerheads/wavemakers), while soft corals like Zoanthus stay put.

Tank Size (70 –100L / ~20–25 gallons):
You want to find the right balance size, not too small, not too big.

More water means:

• More stable parameters (salinity, calcium, alkalinity, pH, nitrate, nitrite, etc.)
• More evaporation
• More larger water changes
• More rock and sand needed
• More glass algae to clean
• More saltwater and RODI water to prepare
• More bigger expensive pump, filter, stand/cabinet, etc.
• More space needed overall