Okay, looking at your profile, I see the connected block at the bottom of the page, so the 148 people in your watchlist who aren't connected may either be people who got separated from the rest of your branch somehow, or unrelated people you created profiles for, or unrelated people whose profiles you've adopted. I have had unconnected profiles in my watch list for all three reasons:
First, I updated some GEDCOMs before the current GEDCOM importing system was put into place. At that time, we were told to skip importing profiles if a profile for the same person already existed on WikiTree. What I didn't realise until later was that, sometimes, the profile that I skipped was the only link between other profiles and the rest of the branch I was importing, so I ended up with lots of isolated profiles or small groups of profiles.
Once I realised what had happened, it took me a few weeks to work through all the profiles I had imported, and search for the existing profile on WikiTree which had prompted me to skip importing the linking protocol. So, for instance, an unconnected profile might refer to a spouse, a parent, or a child, but there isn't a link to that person's profile from the profile on my watchlist. In that case, I'd search for the "missing" person on WikiTree, sort through the resulting hits and check to make sure that I had found the right one, and, once I did find the right one, I'd link my the profile in my watchlist to the profile I found.
For example, if Hannah Slade had somehow gotten disconnected from her husband Isaac Inglefield, then, once I found him again, I'd edit her profile to add a husband, put his WikiTree ID (Inglefield-19) into the box that says, "If the spouse has an existing WikiTree profile 
enter their WikiTree ID here:", then click on the "Add Spouse of Hannah Dorothy Slade" button. Once I do that, then she'd be connected.
Second, I have a bad habit of getting interested in notable people. I'll read about somebody in the news, or on Wikipedia, or wherever, get all interested in them, and create a profile for them. But then, it often takes me forever to build out their branch far enough that I make a connection to the main tree. Some people have memberships on paid sites which can help them trace out connections much faster, but I'm not on any paid sites, so I just end up following whatever leads I can turn up until I make a connection. (A couple of times, it has taken over a year of on-and-off effort to get a notable connected.) So these days, I try to restrain myself from creating profiles for notables anymore. (Not always successfully, I'm afraid.)
Third, there have also been times that I have come across abandoned profiles for people with a family name that's in my family tree, so I sometimes adopt those, try to source them, and see if they're related to the people in my family with the same name.
In both of those cases, I follow the hints listed on the Connectors Chat page: work out the branch, following leads as I find them. If I find a marriage record for somebody, and the person they married doesn't have a profile connected to theirs, I search WikiTree to see if they already have a profile, and create a new one if they don't. The same thing if I find a census record listing parents, a spouse, or children of that person. In some jurisdictions, death records include the names (and sometimes even place of birth) of the person's parents, the name of their spouse if they were married, and sometimes the name of a child if they were an "informant" for the death registration. (I love the death records in British Columbia: they contain so much useful information like that!)
Then, once I've add all the parents, siblings, spouses, and children of the person I started with, and see if I can work out farther still: parents and/or siblings of the parents, spouses and children of the siblings, parents and siblings of the spouses, spouses and children of the children, and outward in all directions. It's tedious, but every new sourced and documented profile added to WikiTree makes that whole tree better and more useful, and eventually, I usually find that final connection to connect the whole branch to the main tree. Then, I go try and find somebody to pat me on the back for my accomplishment. 
