You did not say if you wanted to learn the pronunciation or the writing of n words a day. In pictographic languages it makes a huge difference.
If it is about the pronunciation, 100 a day can probably be done (it's just a matter of training your memorizing skills) ; the hard part will be to remember these 100 words for more than a day or two.
From my experience, the best way to remember vocabulary for a long time is to use it in sentences, so you'll have to spend time talking to someone (or to yourself) (preferably about something that makes sense
)
If you want to learn to write n words a day, I think it is more tricky. If you truly want to learn the language, the best investment will be to study the
keys/radicals used in the Chinese characters. This will be tedious as you will have the feeling of cramming useless symbols, but once you master them it will make the future learning much more structured and easier.
Some people find flash cards useful ; I don't like to use them. When I buy them ready-made I find they don't help much, and they are way too time-consuming to make. I like to "mentally write" the caracters - it helps memorize both the caracter and the order of the strokes, and is faster than actually writing.
As said before, the number of words you can study per day will depend on how, how much and how long you study daily.
I did an intensive Japanese program a few years ago : 4 hours of class by groups of 10-15 with a native teacher + 2 to 4 hours of homework every day.
With this rythm I memorised about 50 words of vocabulary (pronounciation) and 10 characters every other day, but once the program ended I forgot a lot of it.