Welcome to the forum 🙂
It's probably been discussed in past threads, so you might find more info in those, but I've yet to hear of a way to increase overall ticklishness on a permanent basis.
But there's certainly plenty of things you can try on a small-scale, temporary or on-going level - wearing different materials, using different tools, have different people tickling you in different ways to see what has the best effect, keep all skin moisturised and soft, compare getting tickled when your skin is hot/cold, dry/wet , create suspense with blindfolds/earplugs, try mirrors and different positioning - eg where you can see your ler only in the mirror, or where you can see yourself and your own reactions. Consider how your own mood affects your ticklishness - good mood/bad mood, nervous mood or showing-off mood (maybe getting tickled in public would suddenly drive you wild?)..... I could probably go on, but you get the idea 🙂
Keep a note of all the variables that made you feel more ticklish than usual and keep doing them!