Chronos. There is rarely a reason to get anything else for Jenos except Chronos if you're intending to heal with him. If you find yourself being hard-countered get Chronos II then buy another item to properly defend yourself.
It’s hard to escape a good Skye. However, she has no mobility aside from movement speed, so if one jumps out at you, Flutter straight up and flick down shots on her before she can lock on again. Use Seedling if available.
Recently, Maeve's Midnight was heavily nerfed - it can be countered by Resilience (at the time of making this) and go down to a minimum duration of around 2 seconds. If the option is available to you, buy Resilience - especially if you're her target.