In my experience, small, occasional gaps in employment are not quite as concerning as they used to be. Recruiters understand the world we live in today where there is a lot of downsizing, closures, mergers, acquisitions, etc. They also understand that people just don't stay with the same employer as long as they used to, for whatever reason. The days of working for the same company for 30-40 years and getting a gold watch at the end are almost extinct. It's very rare these days, where most people change companies every 5 years or so.
So recruiters do expect to see more moving around than they used to. If you've changed employers quite a bit and have a few months in between some of them, it's likely not a big deal. Where it becomes a bit troubling is when the gaps are big or too frequent.
If you've been off work for many months, or even years, it may be helpful to explain it somehow in your cover letter or resume. I don't suggest having a formal "Reason for leaving" line in your work history, since you don't want to draw attention to it, but you can subtly include certain reasons for being unemployed, such as resigning to care for an ill family member. That may help alleviate any concerns the recruiter may have about your employability.
Jumping around too often may be a concern as well. Yes, recruiters expect to see it more often than they used to, but there's still a point where it becomes a reason to pass you by and move on to the next applicant. On-boarding and training is a big investment for most companies and they don't want to make that investment if you're likely to be out the door very quickly.
The bottom-line is everyone is out of work at some point in their careers. Stuff happens, whether it's by your own doing or out of your control. Decision-makers realize this. Just make sure it doesn't become so long, or so frequent, that recruiters start to question your ability to commit.
Best of luck!