Honestly I disagree with some of the other posts in this thread. I think it's more than fine to be playing on multiple sites & in fact I'd recommend it (why limit ourselves to the games on just one site?? Makes no sense to me).
Its fine playing on multible sites, when you have already established yourself as a winning player. But if you are playing the very lowest stakes like 2NL cash or <$1 average tournaments with a $100 bankroll and trying to make it grow, what is then really the purpose of multible sites? Are you going to table select across sites at 2NL? Like really?
And also what are you going to do, when you lose all your money on one site? Withdraw $20 from another site and deposit, so you can play there again? If not you quickly end up playing, where you coincidentally have money. And then why not instead make a deliberate choise and play on the site, you like the most? Another thing, that might happen, is, that you end up being very focused on bonuses, challenges and freerolls. And while these can help you make a bit of extra money, they do not help you improve your game.
I think it's important to be playing 'similar' games though... especially if you are fairly new to the game (first year or two playing poker). You want to focus on one game type to get accustomed to the structure and how to play it & of course watching how others (the better players) are playing it too.
Its important to focus on either cash games or tournaments, since they are very different games. In the very beginning you might need to try both to see, which you prefer, but then you should make a choice. Of course you can always change your mind later, but you should not move back and forth every session or every week. And going back to my previous point about challenges its not great to spend time on cash games, just because there is a promotion going on, if you have decided to focus on tournaments.
As for further specialisation it might be ideal to only play 6-max or 9-max cash games, if you are a cash player, or only play 1 SnG format, if you are a SnG player. But you need to try different formats to find the one, you like the most. And in todays climate it can be difficult to get enough action, unless you play on the largest sites. Even on PokerStars SnGs dont run that frequently any more, and after the latest rake increases you definitely want to look at, how much each game type is raked.
Some sites are much softer than others. Currently the softest site I am playing on is WPTGlobal. Unfortunately it also has the worst software (lol) but if you can get it set up and get accustomed to it, it'll be well worth it. I actually don't even play on the site that often (a bit of cash games late at night) made a small deposit ($40) to qualify for a CC promotion on there and now have ~$900
I personally play mostly Cash games but a small amount of tournaments as well. (sites that have soft cash games also have softer tournaments).
The cash games play significantly different on differing sites.
in order of easiest to hardest:
WPTGlobal
SportsBetting/Betonline
888Poker
Partypoker
ACR/WPN network
GGPoker
Pokerstars
If you are going to pick just one site to build your first bankroll, it can definitely make sense to pick one from the top of this list rather than GG Poker or PokerStars, where everyone else play and therefore also most of the good players. There are other considerations also though. 888Poker has a very high rake for 2NL-5NL cash for instance.
Another thing to consider is which days of the week are softer and what time of day is softer.
Generally speaking, I find Fridays to be the absolute best, followed by Saturday and then Sunday. (weekdays have fewer players and larger ratio of regulars vs recreationals).
This is true. But if you are trying to become a winning poker player, you probably still need to put in a few hours of practice most days, even though games might not be super soft on weekdays. Time of day is also important with the asian time zone evening hours being the worst at least on PokerStars.