Just as an FYI, in the PHB doing a spell as a ritual adds a flat 10 minutes to cast time, rather than 10 minutes per level. I don't feel like ritual spells would impact the balance too much. I would basically break them down into knowledge and utility. For knowledge, there are a bunch of ritual divination spells which I'd mostly have access to anyway that let us get some kind of one word answer or sign from a deity in response to one or more questions. I've never had much luck with divination spells, and don't tend to use them. Then there are the ritual spells that can give me more direct and specific knowledge, like Commune with Nature and Speak with Animals, which can let me find out things about what's around us. Locate Animals and Plants, Detect Poison and Disease and Detect Magic, which can let me know about those things, Identify which lets me know the properties of a specific item. And Comprehend Languages, which lets me understand any language I hear or read (as long as I touch what it's written on). Then there are the utility spells. There are the spells that let us send messages in weird ways (Magic Mouth, Animal Messenger, Illusory Script). More protective spells, like Leomund's tiny hut which creates a magic house for us to sleep in and Alarm, which can warn of approaching bad guys. There's a couple that might let us go places we couldn't otherwise (Water Walk and Water Breathing). There's a couple that wouldn't have any impact on battle or anything but that I'd really enjoy in Find Familiar (so I could have a bird of my own, would be useful for scouting since you can communicate with it telepathically) and Phantom Steed (just to increase how much the elf judges me). The only one I could seem impacting a fight, if we somehow were able to know someone was coming and prepare in this way or (even less likely) find it worth it to cast in the middle of a fight would be Silence. In the aftermath of a fight Gentle Repose might be used to keep a corpse from decomposing so it's easier to bring the person back to life. Then there are the other spells (Tensers Floating Disk, Unseen Servant, Feign Death, Meld into Stone) that I struggle to find any real use for. If I will have access to Find Familiar my character will definitely be looking for any opportunity to obtain "10 gp worth of charcoal, incense and herbs that must be consumed by fire in a brass brazier" and if I can use Identify, we'd all probably want him to get "a pearl worth at least 100 gp", since that spell can be incrdibly useful, especially in a campaign with demon amulets all over the place.