Is this kind of bad foreign English or it would be correct to say "to keep yourself up-to-date"/"informed" when subscribing, e.g., a twitter or a RSS feed? Is there a single verb/adjective/shorter synonym for saying your knowledge is constantly updated/on a current level? Is there anything suited for keyword/tag usage?
"Staying/keeping informed" works well, but most often when someone is trying to specifically describe that they take strides to keep their knowledge up to date, they say that they "keep abreast of [the topic]".
Less formally, you can say you're "plugged-in to [the topic]".
"Staying current" (on some topic or with some source) is a pretty common expression in my experience (US, tech community).
For knowledge of a topic "stay up to date" would be fine.
To name a button a more active word such as "follow" or "track" might be better.
Keep up: "I try to keep up with current tech."
Stay abreast, remain cognizant
If you use stay up to date, it seems susceptible to the misunderstanding that you're staying up late to date someone.
Edit: I suggest that you use "keep yourself updated with latest information" or "stay tuned with it".