Let me explain how ritual spells work because they're actually quite different from your regular combat magic (and understanding this can really change how you approach different situations). The neat thing about rituals is you can cast them without using up spell slots when you're not in combat, which saves those precious slots for when you really need them.

There's only a small collection of these special spells - things like Detect Thoughts and Find Familiar (keeping track of which ones are rituals will save you a lot of headache later). Something interesting to remember is that these spells lose their free casting benefit if you try using them during combat, so timing is everything here. Most ritual spells are designed for exploration and utility rather than fighting (they're particularly useful for scouting or preparing before big encounters).

Here's something that might help - any class can actually learn ritual spells through the Ritual Caster feat when you hit level 4 (this gives you access to two ritual spells from either the Cleric, Druid, or Wizard lists). The smart way to use rituals is to cast them before you think you'll need their effects, since they often last quite a while. For instance, you could use Longstrider to boost movement speed before heading into what looks like a dangerous area (this saves your actual spell slots for when things get dicey).