Combing with Neco Arc can be hard becuase of her short range. However, she hits decently hard, and her j.2C can be painful. All damage is no counters on W.Len.
2abc 5c j.abc j.abc airthrow. 3847 damage. 83.5% meter. You can't do much off of airthrow, so this kind of sucks.
2abc 5c j.abc dj.abc2c. 3799 damage. 86.5% meter. Techable, but if they don't tech...
Midscreen: land, 236B. A bit more damage and meter. 4094 damage, 89.5% meter. Looks cool when they fly into the beam.
Corner: jump up again and hit them with an aircombo. Do whatever followups you like. Can break 5000 damage.
2abc 5c j.bc dj.bc 236C. 3680 damage. Gives you oki. Yay, oki. Maybe you can OTG but Neco Arc is awful at OTG. You can do j.abc dj.abc but it's hard, and only like 80 extra damage. Try it if you want.
Combos with Neco Arc are far easier if they start with 2B. Keep that in mind.
If for whatever reason you hit with 5B on a standing opponent:
5B j.C dj.BC follow up. You need to delay that first j.C a lot. If you do an airthrow, do dj.ABC so you don't rebeat.
6ABC uses the 5B to launch, so treat that as a 5B combo. Jump straight up midscreen or you will go under the enemy and that really isn't good for you unless you are doing all sorts of crossunder swapside shenanigans with j.B, which only work sometimes and not overly reliably. Seriously, just jump straight up.