It is very simple you can do these only:
1-select your coins
2-check it's valume and market caps u can use coin marketcap.com
3-find it's market using coinmarketcap.com
4-signup the exchange that you find it from coinmarketcap.com
5-buy it.

Actually it is a simple answer. There are many exchanges that exist today, whether it is based on national and some are internationally based. as you say there are some exchange that are indeed concentrating in their country of origin. The difference is the trust and security of the exchange, yes in this world security becomes important because a security will determine what happens to the funds we have. For the moment I really trust bittrex as a top choice, in addition to a user friendly look, bittrex also assures very secure security. Security is a must-have thing and I do not blame the fee on bittrex because I think security is a very important thing and can not be compared with a small amount of money.

You can find every altcoin you want on coinmarketcup site. There they write where you can trade it. Which echanges. Go there, register, put money on ur account and you can trade

before you start buying you should check first at coinmarketcap. there are many altcoin found and also listed exchanges in each altcoin. and at least you see a chart of price movements

Open accounts on exchanges, deposit BTC or ETH and trade. As simple as that.

In buying altcoins you need to do it in the crypto market exchange like hitbtc, etherdlta, kucoin and other known crypto exchanges.

First you need to decide on the stock exchange. The largest: Binance, Bitrix. Now the registration for them is closed, you need to wait for the opening.
If you want to first buy altcoin, you need to choose which altcoin you are going to buy, and then go to the stock exchange

I'm new too,i buy coin from Yobit,i think is very transparent and easy for use
Also,my friend buy altcoin from Yobit,he said that he will continue to buy over Yobit