Let's see, depends on what type of a build you want. Tank + Offense? Technically you can build that off Paladin Tank skills while using RG offensive skills. Rapid Smiting can deal a considerable amount of damage to single targets early on, or you can go the more typical pure auto-attack Crit and nix any offensive skills in favour of grabbing heal.
Here's a build based around speed and tanking, no healing though, with my personal picks for Spear skills, and 10 points to spread some love. Get more prestige, go for the Shield attack (Press CAN do decent damage), get Exceed Break (which I consider a maybe in a spear build, counter to a lot of RG builds I've seen). Heck, if you wanted, you could still get Reflect to use in spare moments when you're surrounded on all sides:http://irowiki.org/~himeyasha/skill4/rgd.html?10Jkoxbxlk1bxGS3bnHNbnaSbpdnadak1
Another build, this one aims for Healing and Spear Skills, with 4 points to maybe put into Guard (helps considering the Platinum skill for Crusaders requires Guard and can be beneficial if surrounded), or you can go for 2 points into Resistant Souls, which is very situational and I have no idea how well it works since I've never used it nor know anyone who has:http://irowiki.org/~himeyasha/skill4/rgd.html?10JkoxcA4kGSHQdnGAHNbnaSbpdnadak1
The thing about soloing a Paladin is...with Spear Quicken and an agi build, it's pretty easy to without anything else. Heck, you could just get Spear Mastery, Quicken, and Cavalier Mastery finished off and go to town. Save the rest of your points to place however you want.
Just in case, if you want a sacrifice build, which literally "sacrifices" the Paladin's ability to function in any other way besides Auto-attack spear and playing the "sacrifice". You can still solo this of course, as per the paragraph above:http://irowiki.org/~himeyasha/skill4/rgd.html?10JkoxcFkFuFakGS5HNbnaSbpdnadak1
However, I see sacrifice, due to the literal sacrifice in your own Paladin skillset (subpar shield skills overall), as making up for bad players who don't want to learn the game =p. Not that it isn't useful, it is extremely useful, especially if sacrificing for the tank (assuming well armoured) and healer/s. I just don't like the requirements and gimping of other skills, especially if you want Spear Skills and any real sense of soloability. Matyr's Reckoning isn't as fantastic in Renewal as it was in Classic (can't hit that 80+% physical damage reduction with armour alone, so it's more dangerous now, nor is it as effective for high damage later on), so even going that route isn't as effective. Spear's are pretty much the best solo builds as a result.
Hope that helps, but I'm sure some people might have a few things to correct me on or disagree with me about.