GBP to USDT? (trying to work out if this is the best way to do exchanges?)

[thegoatiest]

Hi,
I'm currently signing up to several exchanges; Binance, Kraken, Bittrex and GDAX

So, as far as i'm aware they all do USDT to cryptocoin. However Bitrexx also accepts USD Deposits.
What's my best bet considering I have GBP? Should i buy USDT then send it to an exchange and trade for crypto. Or should i use USD on Bitrexx getting charged to pay in a non sterling (GBP) transaction e.t.c.
And is tether.to the best place to buy USDT?

Thanks!!

I'm pretty confused tbh, been reading about exchanges for about 12 hours straight.