Predator and Conqueror runes would be considered the main default options.

[*] Predator for stronger ganks, great snowball potential
[*] Conqueror for better mid/late game teamfights and jungle farm focus

The other rune pages are for specific builds/styles.

[*] Jak'Sho, The Protean - Great tank item. Generally good for most situations. Scales very well into late game.

[*] Evenshroud - Fairly good stats, but increases damage you and team does by 10%. Great option when bot and/or mid are fed.

[*] Riftmaker - Decent when on an early lead. Grants AP, true damage, and omnivamp. So can be a good option.

[*] Radiant Virtue - Team fight innitiator. Whole goal with this is to ult with team and charge in. Grants bonus damage with demonic due to increased health, heals a large amount for whole team if together.

[*] Hextech Rocketbelt - Dive option. Similar purpose as Radiant Virtue, but much more greedy. Only to be taken if going AP focused, have a lead, and the enemy carries are very ranged with a ton of peel.

[*] Rod of Ages - Overall solid option. Though it is far more late game focused. Mythic is almost always 3rd option on sing. Which makes Rod of Ages not hit full stacks until late game. Sing isn't the most late game focused, so normally better options. Can be good if incredibly fed early and not able to close the game out early/mid.

[*] Liandry's Anguish - Can provide great burn damage, but lacks in utility. Doesn't give defense, sustain, mobility, or similar. Only damage over time. Good against HEAVY HEAVY max health team, otherwise other choices end up providing more usefulness.

[*] Crown of the Shattered Queen - Grants movespeed and AP from mythic passive, which sing loves both. Good stats included too. The passive is great for diving in, but it is very short. Can be useful to flip someone, then use the movespeed to get out quickly.

Press Q and run.

Force of Nature and Dead Man's Plate are solid defense with movespeed which is great.
Frozen Heart and Abyssal Mark are generally better for their passives and being more tanky.
Force of Nature is not much weaker than Abyssal Mark, but Frozen Heart is much stronger than Dead Man's Plate
Gargoyle Stoneplate]] can be used lategame if going Jak'Sho mythic and 2 defensive items, selling demonic or rylia for it.