I have been asked a number of times how to repot a cactus or succulent, so here are my suggestions. There is no guarantee because much depends on the species as, as in the garden, not all plants like the same conditions. Cactus also have species that like acid soil and others that like some lime.
The first consideration is that all potting medium must be free-draining, that is water will run immediately straight through the pot. Don't stand the pot in a saucer to compensate; they will have had enough water.
Grit is the best material to add to the soil to make it free-draining. The addition of perlite also helps to aerate the pot.
I use John Innis no. 3 for the soil/loam. This seems to suit as I only normally repot after 2 years. There is long-term food in the number 3 and it is also stronger which, I think, compensates for the leaching due to the rapid water loss.
The normal mixture that I make up is 60% loam/pearlite and 40% grit.
For some species I might add a small amount of peat to make the mixture more acid.
Plastic pots are possibly the best as
a cactus can be very heavy in its self and with the addition
of 'stones' in the soil, it all amounts to a heavy pot. Plastic
also means that it does not dry out too quickly. Some plants
require that to happen and so are then potted in old fashioned
clay pots where the water and air exchange place through the
sides of the pot.
Some plants will flower when young and small and others take much longer i.e. from 5 years or more.
Some of the plants that will flower on a windowsill are Rebutia, Mammillaria, Lobivia. If you see these for sale and want success they are the plants to try.
In the succulent world it is harder to
give names of 'flowerers' but some Aloe, Echiveria, Crassula,
Kalanchoe and 'living stones' Lithops will flower.