I think from what you've said about the type of game you enjoy you should have fun with the first 3 Divine Divinity games.

Divine Divinity has a lot going for it in relation to gameplay, characters and the story. You will meet some memorable characters, quests are varied and not always combat orientated, plus the story draws you in from early on. There is plenty of combat action but this is comfortably balanced with exploration and conversation. I consider this balance is there for all 3 of the first Divinity games. Also in each there are quests that don't require combat.

In Divine Divinity you have 3 main classes to choose from at the start but you will probably find you end up playing the game with something of a hybrid across at least 2 of these. Also, there is a fun Easter Egg in this game.

Beyond Divinity is my least favourite - I felt it tried too hard and just didn't have the narrative drive of the first - however you will find people who love it just as much as the first game. Also having to play in tangent with a Dragon Knight who was tied to my side didn't work for me.

Divine Divinity II - Ego Draconis is a completely different game to the first 2. Divine Divinity and Beyond Divinity are isometric whereas this is over the shoulder within a certain range. The graphics are stunning. What I did feel was especially good about this game was how it continued and developed the story from Divine Divinity. There are a lot of narrative and in game references to Divine Divinity, a few to Beyond Divinity. In addition, you get to fly and fight as a dragon - a part I really enjoyed.

If I was to recommend a starting place to explore the Divine Divinity universe I would say Divine Divinity - start at the beginning. It's a super game that still puts a smile on my face despite how many times I've played it through.

The atmosphere (including music), world interaction and quest design (for the time) were what most appealed to me when I tried the demo before the original disk version of Divine Divinity was released, and the humour (particularly an encounter in the starting town's catacombs) made it a day one purchase for me.
The start of the game and the end are combat heavy, but for most of the game I could switch between combat / exploring and non-combat quests and NPC interactions depending on my mood. The combat at the end of the game can mostly be skipped.