Link has a lot of complicated tactics. The important thing to keep in mind is watch your spacing; it the opponent can hit you, don't use a projectile then. Try to not let them get closer than the tip of Link's sword and use the right attacks for the right spacing. From close to long range it goes sword attacks, grab/Zair/bombs, arrows/boomerang/bomb pull. Use the right attack at the right time before you move on to advanced techniques.
Link has 3 projectiles in addition to close range attacks so keep moving and pressuring the opponent. A lot of beginner players wait idly. You should try to play fast with a lot of pressure for the right spacing.
Some bread and butter combos are Dthrow>Fair is guaranteed on several characters. What followup works depends on the %s but a good rule of thumb is if the opponent is at: 10-30% Utilt or Usmash, 30-50% jump and Nair, 50-90% jump and Fair, and 90%+ jump and Uair. Here's a specific chart of what works on what characters:
https://docs.google.com/spreadsheets/d/1VC-qvEWaQhgqR7MfMMGaTNyMiTQzXWDJGXpR__Uuzks/edit#gid=0
Bomb forward throw>Fair is usually really good. You can get even more combos from bombs by throwing on down from above or Z dropping them. Later use bombsliding when you're comfortable with the basics.
Other possible combos or "chains" (not true combos but work depending on what the opponent does) are:
Jab, jab, and cancel the 3rd jab into a followup like upB or possible roll/jump away if you're hitting a shield or not safe. Dtilt>hop and Fair can work sometimes. Zair>land and buffer jab. At lower %s Nair/Fair>land and jab or quick ground followup. Nair>uncharged arrow can "lock" opponents who bounce on the ground, what this means is they will only be able to stand without rolling or attack so you get a free Fsmash punish. The first kick of Bair has no knockback so you can land before the 2nd kick and combo into upB or turn and jab.
If you have trouble remember Utilt has wide range, low startup and lag, and can KO after 130-150%. Really nice and simple option.