Since getting my 2nd hand CTX (Or 3rd hand rather - Gentile use) - I use a Stereo to AUX Adapter and use ANY and ALL standard 3.5mm Aux headphones. Personally, i love using earbuds. Hoodie On, Ear buds in - just like horse blinders for those spectators who love to watch us in action. Shovel wise, I like my Canon garden shovel with an extendible handle. Small head but perfect for 6-8" plugs. And at 14$, i dont mind replacing every few months. As for bags... Personally I never leave mine anywhere but on my shelf @ home, so no bag needed - And being a larger detector it will require something of decent size.
I have the 11", 17" and Tiny 6" coil - all of which have their place. 11" for standard parks (great depth and stability on most targets) - 17" for DEEP ground or items bigger than small hunks of foil (Minus it loves balled up gum wrappers made of foil) and the 6" trashy park coil. Only gets 6-8" but its AMAZING for separating targets.
All in all.... the BEST tool to get yourself.... The Andy Sabisch CTX 3030 handbook. You are doing a lot wrong if you ONLY read the manual. Gives great tips - super easy read - lots to go off of and if you are already hunting with a 3030 and you read this after - your whole game will change and you will want to revisit ALL previous sites =)
Hope this helps!
Bquamb