I'm a newbie D&D5e Wizard player and was intrigued by the Ritual tag and its major benefits for Wizards.
I'd like to ask if a Ritual Spell in my Spellbook can be cast multiple times a day, without the need for a rest, assuming I have plentiful components to cast said spell?
Each ritual adds 10 minutes and most spells take 6 seconds1, there are 60 minutes in an hour, 24 hours in a day so 144 lots of 10 minutes, lose just under 15 minutes for the normal casting time so 142 is the maximum. This is likely to be “as many times as the wizard wants” unless his wants are excessive.
Kidding aside; your understanding of what a ritual spell is is correct - a spell that can be cast unprepared from your spellbook as long as you have the time and components. You do have to concentrate for the full casting time (and the duration of the spell if it is a concentration spell) so your casting can be interrupted, however, you can just start over once the interruption has been dealt with.
1If you are using 1 minute spells then 130 is the maximum. For 1 hour spells then you are down to 20 but if you are losing 19 familiars in a day please be more careful with them - this is why we can’t have nice things!
Certain spells have a special tag: ritual. Such a spell can be cast following the normal rules for spellcasting, or the spell can be cast as a ritual. The ritual version of a spell takes 10 minutes longer to cast than normal. It also doesn't expend a spell slot, which means the ritual version of a spell can't be cast at a higher level. (Basic Rules)
Since ritual spells can be cast without using a spell slot, a wizard is limited in how many they can cast per day only by time (normal cast time + 10 minutes per cast) and any costly components used in the spell.
Since this way of casting bypasses a caster's normal limits (spell slots), most ritual spells are either not all that impactful (or at least not that impactful when cast multiple times), or use other methods of limiting their use.
Detect Magic, for instance, is a useful spell, but probably doesn't see a use more than once or twice a day.
Tenser's Floating Disk can create multiple carrying disks if repeatedly ritual cast, but each only lasts an hour, putting a limit of 6 simulaneous disks per ritual-casting wizard.
Find Familiar, which you mentioned, explicitly says in its text:
You can’t have more than one familiar at a time.
So to answer your question: the ritual casting feature does not limit how many rituals you can cast - but you will rarely find it useful to spam rituals.
