LoN bombardment isn't good for starting, its very hard to gear. Just go for standard invokers thorn's build. It's not as good/fast as LoN bombardment but its still decent and it is very tanky and easy to play. You can find it at the top of dfans, it's the one with highest votes. You don't need any ancients for it to work, you don't need any specific weapon. For lower torment's you just need 2 invoker pieces. For farming t10 you will prolly need 6 set pieces and some additional items.