Its entirely possible to do both! Casting a ritual requires usually about 2 minutes of “appropriate roleplaying”, what that is is left vague and can be almost anything. Drinking mysterious arcane liquids, breathing is dank smoke and reading Empire Tarot cards is peak Kalevese mystic.
TLDR
The only difference is that to have a mechanical effect you need to expend a resource called crystal mana and you can only achieve specific effects. These effects, or Rituals, have a magnitude, generally how powerful the ritual is. The more powerful the effect, the more fuel and magician power needed to power it. It is possible to cast rituals solo, but at a certain point you need other people to cast the ritual with you as the ritual is too powerful for one person to handle, this is called a Coven. The plus side is that a group of people can perform more powerful and impressive effects, the downside is that they can only do it twice a day. Solo casters are more restricted with what they can do, but they can cast as many rituals in a day as their hearts and feet can take 
This is where ritual ranks come it. It represents how knowledgeable and capable your character is at casting specific types of magic. The higher this is, the bigger the magic you can do on your own.
there are six types, or Realms, of magic:
Spring
Summer
Autumn
Winter
Day
Night
Here is a general overview of them, and if you click on the emblems it gives you all the details of each. Autumn, Winter, Day, and Night have divination rituals but Day and Night have the most and most useful of them. Night divinations are weird and metaphorical and must be interpreted, while Day tells you precise facts. Day will tell you how many troops are in a territory, but it wont risk lying to venture a guess as to the future of where they are going next, unlike Night.
However, there are other ways of making it possible to do higher level rituals solo.
Mastering a ritual makes each crystal mana you spend on a ritual count as two, what that means is that a mastered ritual is half the cost and your ranks to cast that ritual are doubled. So, if you have two ranks in Day magic then you can do at max a magnitude 4 ritual.
Better, but still not high enough to do most divinations, let alone the decent and juicy ones. This is where buffing up your “effective lore” comes in. There are certain items, potions, rituals and places of power (Regio) that can make it easier for you to perform rituals. However, effective lore can only be 3 times your “base” lore.
So, in our Day lore 2 example; if you drink mind altering potions, wield a staff that whispers dark secrets, and get a ritual that lets you see time and magic, you can cast a mastered ritual by yourself up to magnitude 12 away from a Regio. Thats quite a lot of extra power! But, in Empire, diminishing returns are a big part of the game design so getting more and more effective ranks is expensive. Realm lore itself is also expensive, 1 rank cost 1XP total, 2 ranks cost 3 XP total, 3 ranks costs 6 XP total, 4 ranks costs 10 XP total, ect.
Final thoughts and ignorable suggestions:
If you want to go the full magic divination route, i would suggest the following starting skills:
Magician: 2XP (mandatory for any magic, also lets you be part of political wizard shenanigans if so inclined)
Day Lore rank 2: 3XP (puts some the best divnations in solo range with buffs)
Night Lore rank 2: 3XP (puts some the best divnations in solo range with buffs)
This gives a decent base, but you still cant cast the really good Magnitude 8 rituals solo. This is were the best divination buff in the game comes in: Crystaline Focus of Aesh. This gives you a +2 to ALL divinations in the game, putting you square in the range for the great Magnitude 8 Day and Night rituals with Mastery, and if you take a Rank of Autumn and Winter later on you can also cast some decent divinations with those realms too.
After your first event i would suggest Winter Lore rank 1. This puts all the winter rituals in range, especially the imminently useful Wisdom of the Balanced Blade because curses are prevalent and cool.
The Autumn divinations are a bit niche and underwhelming, but if you want to be completionist 2 ranks of Autumn lore will put all the divinations in that realm in range
Here is the problem, Crystaline Focus of Aesh is EXPENSIVE. If you take a mana site, the resource that makes ritual fuel every event, then you could only afford to have this done every other event and it would take almost all your money so no beer or cookies or trinkets.
So, here is my last piece of advise and i implore you to consider this one most of all even if you rightfully ignore the rest, find a group/ Hall! Groups in Empire are OP by design, the more people something has the better off it is exponentially. Im sure there are many groups on the field that would absolutely love to have a dedicated specialist diviner, especially those that go on a lot of plot quests/ skirmishes who want to not set off magical traps of get killed by preventable zombies. Or groups that deal with a lot of magical stuff in general. They could spread the cost around lots of people so that you could have plenty of resources to do your thing.
But, most importantly, it gives you other people to interact with, to generate lots of fun interactions and game for everyone, and maybe even friends OoC
