I have done the journey several times in the past, but not for a few years. It's pretty simple by train, although you may need to change a couple of times. The cheapest option used to be the coach from Victoria. However, unless you are really hard up, I wouldn't recommend this! Very slow and very uncomfortable.
It's hardest at the start. Once you have climbed up a bit it gets easier. Don't try and avoid it on either side, as you will end up on more difficult ground further on. There is no "best" route, it's climbable almost anywhere at about the same standard. It can be significantly harder kif the rock is wet, as it tends to be greasy.
Probably the best advice I can give, is if you were intimidated by it, try and go up with someone who has climbed it before. I have done it a couple of times with my children. The first time when they were about 8 and 10. They managed OK, but I was on hand to show them how to climb it. Almost all the difficulties are short and above big ledges.
Have used the Cwmrhwyddfor site several times over the years. Generally OK, but facilities very basic if that sort of thing worries you. However, our last visit was spoilt by a load of very loud Scousers which were pitched next to us.