Just don't be too greedy and include the recommended fee.
A few cents is not worth the frustration of waiting for hours or even days imo.
I always pay even over the advanced recommended fee..I accidentally spent what wasn't confirmed, so got an ingoing and outgoing transaction still unconfirmed..I sent message to Quickseller but unfortunately had as of yet no reply, so looks like either my btc will be lost again from the blockchain or I might be lucky to get it pushed through.. so far no luck, feeling a bit despondent now.
I don't know what is happening but many people have the same issues these days, including me. Yesterday I sent the funds as usual with recommended fee, it's been 24 hours now and stll nothing. And the number of unconfirmed transactions on blockchain is huge. Hope the coins are not lost or stolen but there is not much we can do I'm afraid.