If it's your first time on osx, or just setting up a new machine, or doing a re-install, there are a few things I install by default. Before you start the software installing, you should think about security first... configuring your firewall and encrypted partition(s). As for the software:
The first thing I do is point my browser to http://brew.sh/ and install it. Go to Applications -> Utilities -> Terminal and paste:
ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
Once that is done:
$ brew doctor
and make sure there are no errors. If you see any errors, search for them online and fix them. After that I install:
Most of these can be installed in terminal from the command line. For example, if I want to see if Sublime Text is there:
$ brew search sublime
$ brew install Caskroom/cask/sublime-text
and it should install. This is a lot easier than searching online, downloading, and installing each.
Every week or two, you should run the following to keep things updated:
$ brew update && brew upgrade && brew cleanup && brew cask cleanup && brew doctor