A good general rule of thumb is that review should make up at least one-third of your time spent learning. This can be divided up per session, per day, or even per week. Here are some examples of how you might divide this up into a routine:
You could do one 45-minute learning session per day, 15 minutes of which is focused on review
You could do 3 shorter learning sessions per day, one of which is focused on review
You could do 6 learning sessions per week, 2 of which are focused on review
To see an example of how these routines can work with Biblingo, check out How to develop a regular Biblingo routine
If you want to dive a bit deeper into the principles behind developing a language learning routine, keep reading! We like to distinguish between three different types of language learning activities: learning new material, review, and fluency development.
Learning new material does, of course, refer to learning brand new vocabulary words or grammar topics. However, it can also refer to learning new senses of words, new syntactic properties of words, new semantic properties of grammatical forms, etc. This can happen through explicit teaching of these things, or getting language input that contains these features by reading or listening.
Review basically consists of additional repetitions of features you have already learned (or begun learning), with the primary goal being increased retention. The two main components of review include quantity and quality of review. The quantity of review or repetitions necessary will depend on how difficult a language feature is (both objectively and for you personally) as well as the quality of each repetition. There are various ways to increase the quality of review, such as retrieval practice, varied repetition, and elaboration. These strategies, and several others, are discussed in depth here: How to effectively learn vocabulary
Fluency development is basically a sub-category of review, where the focus shifts from retention to increasing speed and minimizing effort. There are four necessary conditions for a fluency development activity: it should be very easy for you, it should be a large volume of practice, there should be some pressure to go faster, and there should be focus on meaning rather than language features.
Now that we have a general breakdown of these activities, we can think about how to balance them. As stated above, a good general rule of thumb is that review (including general review and fluency development) should make up at least 1/3 of your time spent learning.
Regarding how to divide up review between general review and fluency development, a good rule is to aim for an even 50/50 split. You could also emphasize fluency development more by scaling it up to 3/4 of your review time (which would be 1/4 of your total time). There is a fine line between general review and fluency, so you don't necessarily need to rigidly divide the two. The main principle is that at least some of your review should be with very easy material with a focus on increasing speed.
These breakdowns are just general guidelines. Many (if not most) language learning activities you do will include a mix of new material and review. There will also be variation person-to-person, so it's important to pay attention to how well you feel you're retaining material and developing fluency with it, and scaling your review up or down accordingly. But these numbers can be helpful when initially developing a routine.