This. The starter sets are all very good values from each company. I use primarily Citadel but Vallejo and Army painter are also good. The only thing I truly recommend is getting a bottle of Nuln Oil and/or Agrax Earthshade. Yes, you *can* mix your own washes but the Citadel shades are magic in a bottle and dry matte. One bottle should last quite a while too.
And I don't really recommend using craft paints if you can avoid it. Yes, you can get a lot of paint for cheap but often craft paints have colors with some really low pigment counts that take a LOT of work to get layered on evenly. Reds, yelllows, browns, etc. This is coming from someone who loves Delta Ceramcoat white. Doing half the coats with better quality paint will make you happier in the long run.
A Warhammer 40,000 Citadel Essentials set is $40, gives you 13 full size size paints, a brush and you get bonus clippers and plastic glue (not for Legion use). Not a bad way to start, but you may find Vallejo or Army Painter starters have a better range of colors for your purposes.
And I also recommend using color spray primer. For Imperials you can stick with black and white pretty easily, but rebels can vary wildly with color scheme so you can grab a color of your choice that the majority of the model will be and use that. I will say again, don't go too cheap. Army Painter sprays, for example, may cost more than a can of Walmart spray paint but you'll get color match options and a surface actually suitable for painting on.