Runekeeper is a fun class, and has a strong set of trait lines. RK (commonly abbreviated) can go either damage in red (fire) or yellow (lightning) lines, or healing in blue line. Relatively speaking, RK is easier to learn than some other classes because it has less buffs/debuffs and fewer skills to use, but there are still some challenges.
Red Line (Cleansing Flame)
Role: Damage Dealer
Primary damage line for RK, viable in all levels of content. Damage is mostly from bleeds, and RK also has good AoE.
This is a good defensive trait tree for red that gives you better usability on Self Motivation and some extra mits. I would recommend this build in 3-mans where mobs can deal high damage so you can help out your healer by surviving longer.
This a better trait line in raids and some 6-mans. You can get max damage potential with Epic Conclusion (Yellow) and Closing Remarks (Yellow) at the expense of Self Motivation buffs. If there are a lot of mob inductions, feel free to trait Fulgurite Runestone (Yellow). I recommend getting the first trait in Fortune Smiles (Yellow) and Determination (Blue) for extra stats. As our gear improves, there may come a time when traiting these is no longer necessary.
Yellow Line (Solitary Thunder)
Role: Damage Dealer
Used mainly on landscape while questing or running dailies/weeklies. Better mobility than red line and faster burst damage, but less damage output in the long run.
This is the best set-up for landscape, as it gives you plenty of stats and defensive capabilities. The only change you could make is swapping out Statically Charged rank 3 (Yellow) for Flashing Images (Yellow) if you like using your bubble a lot.
Note: There is a niche trait tree you can make to get an AoE bubble, but in the current set of instances, there is no reason to trait this way. I will add it here if it becomes necessary.
Blue Line (Benediction of Peace)
Role: Healer and Support
Blue RK is currently very strong because of it's high healing output, DNFs to quickly revive important players, and its debuffs. Used in all instances.
This is a good baseline trait line for blue. There will be some variance depending on the instance. For some instances, like Dhurstrok, I would replace a rank in Mystifying Flames (Red) for Fulgurite Runestone (Yellow) for the stun and AoE interrupt. If the raid will involve a dps race, then it will be worth it to get an extra point in Mystifying Flames (Red) from Cutting Remarks (Yellow), which will help group damage sacrificing your healing capabilities. If your outgoing healing is capped at 90%, swap out Determination (Blue) for Light on One's Feet (Blue).