When you are a new player here, it is recommended that you first get yourself some gear before trying to get into a faction. A lot of faction leaders are reluctant to let random new people without any items into their faction, as there is a big chance they will be betrayed. If you get yourself some diamond armor first, there's a way bigger chance you will be let into a faction. When posting a new topic, it is useful to also include the things that you are good at, and any past factions you have been in(if you have been in any). It is also recommended that you add something about yourself, and whether you have communication programs such as Mumble, Skype and Teamspeak. Also include a screenshot of your inventory, this way it's easier for other players to see the items you have. If you aren't let in the first time, don't let that put you down. Just get yourself some more items and try posting again a few days later, or ask faction members if you can join them in-game.