I have two favorite feet for quilting in the ditch. They each have a "thingy" that lines up in the ditch and pushes the fold enough out of the way that, when you get it straight, the stitches disappear. Neither one takes very much practice.
(1) There's the "official" in-the-ditch foot: (photo of mine below) (link to a description and list of instructional files: http://www.sewingmachinesplus.com/P60702.php ) This foot works very well, but it can be a bit difficult to see where the needles is going in when you want to position it at the beginning of a "run". This one works best when the fold (press) is to the left.
(2) The second foot, which is supposed to be for blind hemming, works even better. It's easier to see the needle, and you can adjust the position of the little "thingy". It works equally well, whether the fold/press is to the left or to the right. I haven't tried it yet, but i'll bet it would be helpful when trying to line up for machine applique, or for blanket stitching. here's a link to a photo of one like mine and instructions. http://www.sewingmachinesplus.com/presser-foot-janome-blindhem.php
I have this walking foot: http://www.sewingmachinesplus.com/singer-even-feed-walking-foot-006185008-p.php
I also have this one: http://www.sewingmachinesplus.com/pd60-421333-S.php
sometimes they help, sometimes not. i use the first one most often because it's easier to put on. They're both fairly easy to line up for a 1/4" seam, and both can be used with a zig-zag or decorative stitch. my biggest complaint is that they're so noisy. all that clacking drives me nuts.
my freemotion quilting stinks out loud, but i get the least hideous results with this foot: http://www.sewingmachinesplus.com/darning-foot-4021-L.php (the rest is practice and determination. i'll get the hang of it someday ... maybe in the next 100 years or so. :lol: ) seriously, it's the only one i've tried that i've managed to produce something that didn't go straight into the trash.
when i bother to use a 1/4" foot, i use either one like this: http://www.sewingmachinesplus.com/singer-foot-386005-p.php
or a clear plastic one (i can't get a good photo, and can't find one like it online.) i've just ordered this one: http://www.sewingmachinesplus.com/P60498.php (it has the benefit of the extra wide platform that covers the feed dogs completely, plus it's see-through so i'd know where the fabric is. i don't see why it wouldn't work on my machine. it looks like a universal snap-on to me. i'll let you know if it's any good.)
99% of the time, though, i use my favorite all-purpose foot for piecing. (similar to this, but i've never found another one exactly like it: http://www.sewingmachinesplus.com/685502008.php) after all these years, i know exactly where to feed the fabric (lined up with the little groove) and set my needle to get the 1/4". i just play with the others to experiment.