For the most part, it’s likely you won’t have to worry too much. Ghost-types dwell in very specific, very distinct habitats: abandoned buildings (typically the older the better), dark forests, very occasionally caves. The basic rule is that if you hear rumors that a place is haunted, it’s actually home to ghost-type pokémon.
Or in other words, ghost-types are easier to avoid than you might believe, so don’t worry.
Should you encounter one, though, stay calm. Most ghost-types feed on fear, and in any case, the more you panic, the less you’ll be able to navigate out of the situation. I realize that this may be difficult, especially if you’re dealing with a phobia, but doing everything you can to keep yourself from panicking is absolutely vital. Take a deep breath and find your center. Think of your body right where it is and concentrate more on feeling your weight than on the ghost-type in front of you.
Once you do this, identify an exit and make your way towards it. Try not to summon any additional pokémon, as that might provoke the ghost-type to engage with you.
If you’re cornered, however, try to remember that most ghost-types don’t actually want to kill humans unless you’ve invaded what’s very clearly their inner territory. Ghost-types are ultimately like any other pokémon in that the ones you’re more likely to see actually want to be around humans and form a bond with us in order to be trained. It’s just that some of them might be mischievous or liable to feed off your fear (which is less dangerous than it sounds, as the consumption of fear actually leaves you in a rather euphoric state or a state of mind in which you feel empty—the latter of which will fade and give way to other emotions over time). Just keep this in mind and, if you absolutely have to engage, try to form some kind of friendship. Rather than show fear, show interest. This may confuse a ghost-type enough to allow you to escape or to get it to leave you alone.
As a note, normally, I respond to asks about fear with advocating exposure therapy, and if you want to get over your fear of ghost-types, I wholeheartedly encourage you to try it too. Find a trainer you can trust who owns a ghost-type and ask them to help you by setting up times to meet their ghosts and spend time with/help take care of them. Start off with a little bit of time of exposure, then gradually increase your time until you can tolerate being around that ghost-type for long periods. This is also a great way to meet a potential traveling companion.
Best of luck, and congratulations on the beginning of your journey!
