apple & mint or gooseberry & mint jelly are both really delicious.
Just gather as many apples as you have available, I usually use crab apples, (under ripe thinnings from your tree would be fine) wash & chop in 1/2 or quarters, no need to peel or remove pips, add a huge bunch of mint, cover with water, bring to boil & simmer to a soft pulp.
Strain through a jelly bag (if you don't have one, line the biggest colander that you have with scalded butter muslin), suspend over a pot or bowl to catch the liquid - it needs about 2-3 hours. Measure the liquid and hopefully you will have a couple of litres (it won't be a lot).
I use between 400g to 500g sugar per litre of extract which makes a very soft set but it tastes much better. You can increase the sugar up to 1kg per litre but that's far too sweet for me. The more sugar, the quicker the jelly will set.
Finely shred some more mint leaves and set aside. Place jars in 100C over to sterilise & scald the lids in boiling water & leave to drain on a clean tea towel.
Weigh the sugar and bring the extract to a boil (by the way, only use 1.5l extract per batch, less is fine but more than that and it can be difficult to get a good set). Add the sugar and stir until well dissolved. Once it comes back to the boil, set the timer for 15 mins. It may take longer but don't over boil or the jelly will be rubbery and have lots of air bubbles.
Plate test to check for setting point or scoop a little jelly into your wooden spoon, tilt it and if the jelly hangs off the edge of the spoon as a little tear drop, it's ready to bottle. Stir in the shredded mint and pour in the jelly to within 1mm of the top of the jar, screw on the top immediately, turn the jar upside down so that the jelly coats the top of the lid and set to stand undisturbed right way up.
Exactly the same method if you have gooseberries.
Do post a photo of your finished preserves!