It's always good to have a wide vocabulary when you first start writing.
As you continue to rap, using words over and over again, simple everyday words will get boring, wear out, and make you seem plainly boring. You need to spice up your vocabulary, which also helps you have more words to rhyme with.
What I did when I was starting out was take the dictionary and learn 1 new word a day, or every other day. It really helped, believe me; though it sounds boring it's just a little thing you'll do for just a short period of time.
But don't rhyme things just because they rhyme. Make sure they make sense, or else you'll end up looking like an idiot trying to sound smart. (Pseudo Intellectual)
And also, using larger words can tie into multi-syllable rhyming (aka multies). They have a larger amount of syllables in them, so if you rhyme "regurgitate" with "burst your hate" it'll have a better impact because they rhyme quite well but rhyming "regurgitate" with "love the hate" won't give such an impact.
Enjoy. I guess.
