I have been doing that since last November, saved a lot of money from buying coffee without all the side affects of having coffee. My focus is the same or more than having coffee daily.

Lookup nootropics, there's a reddit forum for it. I take a combination of caffeine, l-theanine, bacopa, and magnesium in the morning, and one caffeine pill in the afternoon.

I'm in Canada, you can get caffeine pills cheap: 100x 200mg pills for <$10.

Visit your local fitness health store, and asked them for stuff for focus. I am sure they can help you.

I've tried it for a couple of weeks in different ratios: 1/1, 1/2 and 1/4 if I recall correctly, also with different types of L-Theanine. Didn't notice any effects.

No, but certain teas have rather high amount or caffeine in addition to L-Theanine. Especially mate. Sadly the only place I knew of near me to get that was Teavana, and they're all closing...

NALT works on my caffeine jitters better than theanine