Can not acces localhost:3000 ruby on rails ubuntu - ruby-on-rails

Question

I have been trying to access or at least show my server in my Rails by running the command rails s or rails server and it does not work:
At first it told me I had to install new gems and to run the command bundle install to upgrade them and I did. It installed everything "correctly".
Now instead, I just get some usage help instead of Rails (for example commands I can use). I thought that Rails was out but I run the command rails new myApp and it does create me one and the bundle installs ok. I just want to start my app and try localhost:port, and that to open my app.
It happens the same when I try to generate something, for example rails g model OneModel (or generate instead of g) and for anything I want to generate. It seems it isn't understanding my commands.
I am noob new to ubuntu and far beyond that new to Rails and ruby. If you can help me I'd be so glad. Here's the output I get:
agustin#agustin:~/Agustin/myapp$ rails s
Usage:
rails new APP_PATH [options]
Options:
-r, [--ruby=PATH] # Path to the Ruby binary of your choice
# Default: /usr/bin/ruby
-b, [--builder=BUILDER] # Path to a application builder (can be a filesystem path or URL)
-m, [--template=TEMPLATE] # Path to an application template (can be a filesystem path or URL)
[--skip-gemfile] # Don't create a Gemfile
[--skip-bundle] # Don't run bundle install
-G, [--skip-git] # Skip Git ignores and keeps
-O, [--skip-active-record] # Skip Active Record files
-S, [--skip-sprockets] # Skip Sprockets files
-d, [--database=DATABASE] # Preconfigure for selected database (options: mysql/oracle/postgresql/sqlite3/frontbase/ibm_db/sqlserver/jdbcmysql/jdbcsqlite3/jdbcpostgresql/jdbc)
# Default: sqlite3
-j, [--javascript=JAVASCRIPT] # Preconfigure for selected JavaScript library
# Default: jquery
-J, [--skip-javascript] # Skip JavaScript files
[--dev] # Setup the application with Gemfile pointing to your Rails checkout
[--edge] # Setup the application with Gemfile pointing to Rails repository
-T, [--skip-test-unit] # Skip Test::Unit files
[--old-style-hash] # Force using old style hash (:foo => 'bar') on Ruby >= 1.9
Runtime options:
-f, [--force] # Overwrite files that already exist
-p, [--pretend] # Run but do not make any changes
-q, [--quiet] # Suppress status output
-s, [--skip] # Skip files that already exist
Rails options:
-h, [--help] # Show this help message and quit
-v, [--version] # Show Rails version number and quit
Description:
The 'rails new' command creates a new Rails application with a default
directory structure and configuration at the path you specify.
You can specify extra command-line arguments to be used every time
'rails new' runs in the .railsrc configuration file in your home directory.
Note that the arguments specified in the .railsrc file don't affect the
defaults values shown above in this help message.
Example:
rails new ~/Code/Ruby/weblog
This generates a skeletal Rails installation in ~/Code/Ruby/weblog.
See the README in the newly created application to get going.
agustin#agustin:~/Agustin/myapp$

Answer 1

You have to run rails s from the project root directory.
eg, If you create a rails application, say rails new my_app, it will create a skeleton application my_app in the current directory. Now you have to cd to that directory to start the server