So I've played Dinger since the day I joined. He is my favourite champion even though he's not a popular one and he's very squishy. But I've learned ways to build him. I hope this way works for you guys

Firstly about Skill Sequence. I tend to get my main 3 spells first. Just to have some damage output and the Grenade helps to get away from ganks in mid as well as flash. But after you do that get your turrets to level 3. After that depending on how your game is going best decide do you want more stun or do you like to tower dive with the missiles. Either way works well. But it varies in game

As for Item Building. I tend to not get as far as a 6th item because the game ends. But there is a wide selection of items to choose to fill up the 6th spot
Holy Grail + Archangel staff + Lich Bane + Abyssal Sceptar
All depends on how the game is going

I hope this works for all you dingers out there!!!