So, heres my build for singed, the basic concept is that if you can make a stat scale with mana do it, first thing you build is tear of goddess and run your q, by the time you die for the first time you should have built archangel staff, buy another tear of godesss to build munamasa (it make not seem like it but you can base attack engage and people wont expect it) the passive wont stack at first but after they turn into munamasa and seprahs its built into the items for 2k mana+, next thing you build is rabbadons to make your trail even more deadly, then you build the item that makes you a beast, the NASHORS TOOTH, it gives you attack speed to make the 200+ ad youll have at this point work extra hard for you and the ~100+ damage the toggle on your murmasa will be supplimented with about 70-100 nashors on hit magic so your base attacks will hit for ~500 before mr and armor, then to top it all of build a spellblade item for after you throw people, i like the iceborn gauntlet because it gives you the most mana but ive had sucsess with the trinity force and lich bane. so by the end of this build youll have 3000+ health 3000+ mana, about 400~500 ap and 200+ ad with a decent attack rate with 200 magic bonus damage to base attacks plus spellblade, you will be tanky enough with a high damage output. like a baus.

pros you a ridiculous amount of damage, while having a high health and mana ratio, cons you wont be as tanky due to no magic resist and minimal armor.