Woodworking

I'm trying to do my very first table top out of hardwood but it proving to be quite the learning curve. I acquired a small benchtop jointer and a lunchbox type thickness planer and I've more or less successfully made my boards. What I'm struggling with now is getting a nice glue up without gaps. My first try turned out so so, and i was afraid i didn't use enough glue so I re ripped the joints with my tracksaw. I think my boards are evenly thick but they seem a bit hourglass shaped if that makes sense. They'reb about 170cm long and they join up on the ends, but there's about a 1mm gap towards the middle on some joints and its too much to squeeze all the gaps together on the panel. I first tried jointing on the benchtop jointer but got horrible results with the small bed. (Could also be lack of skill as this is all new to me). I then went with a tracksaw and parallel guides instead,which is better but still giving me a bit of a gap. So I guess im asking how more experienced woodworkers would proceed.

Would it help to glue up two boards at a time so there's maybe enough strength in the clamps to squeeze the gap shut. Or should i rip the bigger boards down so they all fit upright in the thickness planer and try to get two really parallel sides that way? I have rollers to extend the beds of both the thicknesser and the jointer but have had better results with the thicknesses. Is there something else I'm not thinking of?