Hey there,
There are several ways to go about this and what you choose will likely depend on your broker. For example, you'll want to keep trading fees as low as possible. So, if you are with a broker like RBC Direct Investing (like I am) where trades are as high as $9.99 per trade, you'll want to likely accumulate enough cash to invest to keep your fees low. I've always operated under the premise that I won't buy unless fees are below 1%, which meant buying in chunks of $1K plus.
However, today investors have access to platforms like Wealthsimple Trade which have NO trading fees. That opens up the possibility of putting that $100 to work immediately instead of waiting. That is a very good option for new investors or those who have limited funds to invest. You can buy 10 shares at $10 or 1 share at $100 and there would be no fees...so it doesn't really matter when you buy. This would likely be the best course of action.
The last thing I'll say is share price does NOT matter. Never focus on cheaper shares regardless of how much you have to invest. a $100 stock can grow just as fast as a $1 stock - the price of a stock has zero bearing on its performance. It all comes down to fundamentals, so never focus on price - it is irrelevant on its own. Unfortunately, investors often confuse price with value and that is far from the case - there is no correlation between price and value. In other words, just because a stock is $1 doesn't make it a better value (or cheaper) than a $100 stock. In fact, that $1 may actually be expensive and the $100 cheap - so again, it all comes down to company performance and fundamentals.
Mat