I'll assume you are throwing this question out to everybody...

I would have to say it depends. I would say at least 2 at a time, ideally maybe 4 or 5. Try to learn some easier songs to build up confidence and a sense of accomplishment. If every song you learn is hard, it will start to feel like a chore.

Always learn the key parts first...main riffs and the chords. Leave the solo for last. If you have to, you can always improvise the solo.

When I was first trying to build up my repertriore, I was working on one song at a time from beginning to end..solo and everything. It bacame a drag. So now I learn the chords first and get the basic rhythmic feel of the song down. You'd be amazed at how much you can "fake" the song with just that. Then there are key riffs, and key chordal elements...perhaps inversions or embellishments are used that are integral to the sound of the song (think Doobie Brothers).

When you approach it this way, you can have a good number of songs in progress. You may have some longer term "projects" going on, such as learning a particular solo to a song that you otherwise know.

Here's an example from my experience...La Grange. There is a LOT of solo to learn. I felt overwhelmed by it at first. So we could play it sooner rather than later, I learned some key parts of the first solo. I got the rhythm part down easily enough. So, rather than spend a month or two trying to get it note for note perfect, I spend a week getting key elements of the solos down and can play a pretty convincing version of it.

The eye opener was when we rehearsed it, I said to my bandmates "don't worry, I'm working on the solo and I'll get it down...I just need time". They looked at me like I was crazy and said "what you were playing was perfectly fine, don't worry about it". In many cases, the audience feels the same way too. Actually, I think many people would rather hear something a little different.