Welcome to the board! You'll find lots of great tips from some very knowledgeable cheesemakers.
Preparing a "mother culture" is fairly straight forward. First, buy a 1 litre box of trim milk (the UHT long life milk, that you can take out camping, etc). This milk has been pasturised to a very high temperature, which kills most of the bacteria (which is why it lasts so long). Anyway, open that and put 1/16th of a tea spoon of your culture in the milk. Put the top back, but not tightly (needs to breath and release gas, etc). Put the box in a warm spot, like the hot water cupboard. Leave it for 24 hours. Clean 3 ice cube trays, and soak in boiling water for a minute. Remove them, and let them cool a bit, then pour in the milk (it will be gluggy, like yogurt) and you will probably get a bit over 2.5 trays of cubes. Freeze them, and the next day remove the cubes from the trays and store them in a zip lock freezer bag. Label the bag with the name of the starter you used, and the date.
When you make cheese, use 2 or 3 cubes. One small pack of culture will let you make a lot of batches of mother culture.
Not sure if you can do this with prop. Shermi, which is used to give swiss cheese it's characteristic flavour and eyes.
To use the culture directly, one usually sprinkles around 1/8 - 1/4 tsp of culture on the milk, let it sit for 5 minutes, then stir it in. A lot of kits have packages of culture sized for one cheese, so you use the whole thing. As I say, if you make this into mother culture, you'll get near fifty cheeses or more from one single cheese package.
You can let cultured buttermilk sit out on the counter for a day to get it to go thick and gluggy and make ice cubes out of that. You can use that to make cheddars, gouda, and other "meso" cheeses (lower temperature cheeses, where the make never gets above 39 C). For makes that go over 39, use active culture yogurt (thermophillic) as your starter (1 or 2 tablespoons for a 10 litre cheese). These will let you make cheeses with decent results, and once you're confident, and have decided on what cheeses you want to make most, then you can invest in the specific cheese cultures for those cheeses (and make mother cultures, etc)