I agree with many here in that only chlorine and some acid are really required to maintain the pool.
Judging from what you say about your pool, I'd start with the following:
-keep in the "leaf trap" (actually called skimmer) at all times the equivalent of 4 chlorine tablets. If you have more than one skimmer, put some tablets in each to make the total
-add to the water some 300 ml of muriatic acid once a week
-FILTER the water with the pump for at least five hours a day, unless you have a very big filter and powerful pump
Then test your pool twice a week and adjust the amounts of chlorine and acid according to the readings and to what you can see with the naked eye. You may also find that you have to run the pump for a longer time, or the other way around, maybe with a couple of hours a day it will suffice.
Be ambitious about the degree of clarity in the water and ph balance you want, and don't give up until your pool looks absolutely sparkling and transparent. It may take you some months, but once you get the hang of it it's not that difficult.
After a while you can start testing your pool only once a week. I don't reccommend that you do it less often than that during at least the first one or two years.
Finally, there will be times when the aformentioned care is not enough. Some circumstances like heavy rain, use by many people, leafs falling in the water, etc. will make your pool's water turn bad in just one or two days. In those cases you should apply a "chlorine shock", which can be done in a number of different ways. This is how I do it:
-take the same amount of chlorine tablets that your pool needs to have in the skimmers (in the example above, 4)
-grind or pulverise them (put them inside a plastic bag and bang on them with a hammer)
-put the pulverised chlorine in the skimmer/s, and run the pump in "RECIRCULATE" for a couple of hours
In a couple of days, as if magically, your water should look great again.
As for the cost of the chemical products, staying in the initial example, if you had to add two new chlorine tablets a day (it will probably be less) you would be using very roughly some 70 tablets a month including two chlorine shocks (unlikely) at around 35 dop/tablet (you may pay some more or some less), plus two gallons of acid at say 100 dop/gallon (not sure now) the TOTAL COST OF ALL THE CHEMICALS should not be much above 2,500 dop/month. During the first few months this amount coud be significantly higher as you have to experiment a lot.
In my opinion it is better to learn for yourself how the pool works, then you will have greater control over all the costs and procedures.
Feel free to ask for any assistance. I wish I'd had some, I had to learn this online and by trial and error. That's why I understand my methods might not be too orthodox. I am of course also open to any suggestions.