I make various combinations of infused flowers and fruit using plum brandy (sliwowitz) or pear brandy as a base since there's a surplus of both in the village and we have a large old pear tree.
Over the last several years these have become popular with visitors:
- elderflower and only a a little lemon peel (it's an accent, not the main act like in limoncello)
- mulberry with some raspberries and/or red currants for an acid note (mulberry is very very sweet on its own, no need to add sugar)
- aronia and cloves
Apart from these three above which some people really fell in love with, the following two are also popular:
- gooseberry
- black+red currant (the black part is very important; also, this definitely does need sugar)
I also make other flavors - limoncello (with optional lavender), nocino, sloe gin which is actually sloe sliwowitz (this is appropriate since the sloe bush = blackthorn = prunus spinosa is the grandfather of all plums), apricot, elderberries and grape... But the ones listed above seem to be the favorites.
Mint is something everybody is very impressed with at the first sip (really strong stuff, I think dentists would be a good target market - local anaesthesia

but somehow it never gets to the third one. I'm told basil can be excellent but I haven't tried it out yet. Black locust flowers were blah which was a surprise because in other uses - syrup, fries - they can be used to the same effect as elderflowers.
In my experience it takes a year for these infusions to become good (remove plant material after 3 to 6 months, then add optional spices like cloves, vanilla, cinnamon, extra sugar if needed etc and let it age) - and two years to become really very good (if the particular combination was a solid idea in the first place).
Anything more can be a bonus or a step back, depends. The character of some flavors really changes a lot over time, especially aronia and nocino. At the moment I'm out of aged stock because my brother recently got married to a Russian girl and the drinks lab took severe casualties

I understand that sloe gin and nocino are supposed to only get better with age and if you come upon a bottle that's a decade old, it's a revelation.
Here's also some things I do NOT like to do:
- Pouring fresh alcohol over already-steeped material to produce a second batch. Why not: because usually a certain fruit or flower or leaf has a varied set of aromas and by the time the first pouring is made, some of them may have been leeched out entirely. So it can easily happen that the new batch will not be close in taste to the original one. Beware.
- Using lots and lots of sugar. Some people really do like their stuff super sweet. But in my experience adding a whole lot tends to drown out the plant aromas and I don't see the point of that.