I did this as a Drow colossus slayer ranger but went through some of the storyline first. I was actually just playing the evil path at first and already wiped out the druid grove before heading to the goblin camp. There are other vendors later on, so you'll have to sell then kill them unless you're talking about just straight up kill-on-sighting the entire game, in which I have no experience with and wouldn't recommend. I think you can leave the ones in the grove alone and kill the leader first, then loot the map, then sell to them and get your items right, then wipe the rest of the grove and take your loot back. The goblin camp has several vendors and so does the Underdark.
Soloing is already hard enough, especially the boss fights and areas with a ton of mobs like the Goblin Camp. I would definitely use the LvlUp mod and any other mods to help you make the game a little more bearable. I believe I was using that and was level 5 or 6 when I could actually kill everyone in the grove by myself.
I'm currently downloading some mods and will be doing a solo Drow run. I'm not sure on the class yet, though. Either Hexblade (the mod works on patch 6 now) or draconic bloodline sorcerer, although ranger was very fun and powerful enough to do it before.
In the old rules you would loose your "ranger" abilities and become a "Fallen Ranger" if you did something construed as "evil". Not sure if 5e enforces that, but as Rangers always used to be good aligned, and they got powers from deities.... committing evil acts would cause those loss in abilities.
