Best to think of Coltrane in three stages IMO, they are neatly defined by label:
a) Prestige. Very accessible tonal stuff, just classic hard bop really. Just buy them all in this nice budget
All His Prestige Albums box. It is a bargain.
b) Atlantic. He's just starting to show signs of stretching out a bit, this work only covers a couple of sessions, but they were so productive they resulted in about seven or eight albums once out-takes etc were factired in. Buy the lot in this
Heavyweight Champion box. Again it is such a bargain it is wrong not to. You will soon realise the correct number of Coltrane albums to own is all of them.
c) Impulse. This is where things start to get very interesting and maybe alienating/challenging later on. It is also a far harder period to recommend from as there isn't a nice box of the whole lot. To start off with I'd recommend
Ballads,
Crescent and
A Love Supreme. After that you should know where to go next (buy them all!) but I'd probably go with
Live At The Village Vanguard first.
If you like jazz you will like Coltrane, he is one of the giants for damn good reason, hence my recommendation to dive right in rather than just a few bits that you will likely have to replace later as the boxes are just so much better value. Everything I've recommended is pretty tonal and accessible, i.e. I've not gone for anything after ALS which is where he really took off on the atonal free spuritual stuff that a lot of people (including myself early on) really struggle with. In many ways it is best to approach it via the historical timeline and follow his career from the start and kind of grow with him.