So, I've started adding some basic root words to my conlang (which now 
has a name by the way, it's called Tamuni). I've encountered a problem, 

I thought it logical to start by creating some simple, one-syllable root 
words to convey simpler concepts, and create derivations and more 
complicated words later.

However, a problem quickly arose: My language, being roughly modeled off 
of Polynesian languages, has a very restrictive syllable structure and 
phonetic inventory. There are only 11 consonants (excluding the glottal 
stop, which words cannot start with), and 8 vowel sounds (including 
dipthongs.) The syllable structure is (C)(C)V, but the only allowed 
pairs are tr, kr, fr, kl, and fl, so when you do the math, this comes up 
with only 136 possible single-syllable words.

Although that is a decent amount, it's certainly not enough to convey 
all the different simple meanings that I would want. Then, there's also 
the fact that single-syllable words are probably likely to have a more 
grammatical function, and that if every single one of those 
single-syllable words had a meaning, then longer words could be somewhat 
confusing, as they might seem to be combinations of two root words, when 
they're really not at all.

So, how many simple, non-grammatical root words should I roughly aim 
for? What kinds of meanings should they be assigned to?