What to do when expecting multiple job offers?

So, to preface, I have a biochemistry degree and graduated last year. I applied to several jobs, all in varying locations, not too long ago, all within my field with the exception of one. However, many of these recruiters reach out at vastly different times and try to move through the interviews so fast. I was extended an offer today for a biochemist role starting at $21.40. However, I have the second round interview with Hill Pet Food and a PharmaLogic company in New York, both of which pay $62k and $83k, respectively. There's also a biochemist water testing position I've applied for that is taking things slower.

Since this is really my first time applying to a real job (I've worked at Walmart since high school), I'm not sure how to handle certain scenarios, but I told them I couldn't accept the offer at the time as I was looking at other possibilities. Is there a better way I should have handled this?