In general enchantments are much more efficient than (non-instant) rituals. While they take more time, they are more vis efficient. Instantly so for Lesser Enchanted and after only a year or two with Invested. They can also be used as a Feature and/or Focus. I would recommend making any you plan to use as a Feature or Focus an Invested Item, so that you can improve it as your lab develops.
Since you can have two activity specialties active in a lab, I would recommend Texts as the second one. While it only helps with learning spells for which you have a lab text, it does improve your ability to write and copy text. If you can start a loop within your Covenant of all the Magi writing out lab text for spells they create this can greatly increase the amount of spells your Magus learns.
Do not neglect increasing your Labs General Quality. While only half as effective and twice as expensive as a Spells Specialty for inventing new spells, it improves nearly all lab activities. The only ones it does not improve are teaching and scribing texts.
Here is my Magus' lab, which was created through play. While it is generally focused towards Item Creation and Text, many of those can be changed to Spells.
One of the items in it is an enchanted sphere (The Sphere of Woven Thoughts) for creating illusions. You will find that an enchanted item is much better than a ritual for creating illusions which can be manipulated and changed, but which you want around all the time. The item can maintain the concentration required for the effect. You could manipulate the Im and Items bonuses to Spells, so something like it could provide Spells +6.
Another item (The Circle of Magical Threads) was actually originally designed to improve the Spells specialty. Sub Rosa #22 has a whole host of additional enchantments which could improve it that I never got around to enchanting.
While nothing in it is lab specific, you might be able to find something you can use in my Covenant Collection thread. There are over 100 different enchantments ranging from simple to very powerful. At the very least it can give you some ideas.