Rbenv wrong gem installation path - can't find gem - ruby

Question

I'm having an issue with rbenv and what I believe is an issue is of require trying to read from my system gems rather than from shims.
I'm trying to create a single script file without the overhead of needing bundle - though I've tried adding a Gemfile and put the script and Gemfile in the same directory.
Reproducible steps:
brew install rbenv
export PATH="$HOME/.rbenv/bin:$PATH" in my .zshrc
Add eval "$(rbenv init -)" to my .zshrc
Source: . ~/.zshrc
rbenv install 2.6.3
rbenv rehash
rbenv global 2.6.3
rbenv rehash for brevity
Close terminal
New terminal:
ruby -v = "ruby 2.6.3p62"
rbenv version = "2.6.3 (set by $HOME/Desktop/.ruby-version)"
which ruby = "$HOME/.rbenv/shims/ruby"
gem env
INSTALLATION DIRECTORY: $HOME/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0
USER INSTALLATION DIRECTORY: $HOME/.gem/ruby/2.6.0
RUBY EXECUTABLE: $HOME/.rbenv/versions/2.6.3/bin/ruby
EXECUTABLE DIRECTORY: $HOME/.rbenv/versions/2.6.3/bin
SPEC CACHE DIRECTORY: $HOME/.gem/specs
SYSTEM CONFIGURATION DIRECTORY: $HOME/.rbenv/versions/2.6.3/etc
RUBYGEMS PLATFORMS:
ruby
x86_64-darwin-18
GEM PATHS:
$HOME/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0
$HOME/.gem/ruby/2.6.0
gem install colorize - this gem seems to work fine
gem install httparty
gem install pry
File header:
#!/usr/bin/ruby
require 'httparty'
require 'colorize'
require 'pry'
./file.rb
Stack Trace for HTTParty
/System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/lib/ruby/2.3.0/rubygems/dependency.rb:319:in 'to_specs': Could not find 'multi_xml' (>= 0.5.2) among 17 total gem(s) (Gem::LoadError)
Checked in 'GEM_PATH=$HOME/.gem/ruby/2.3.0:/Library/Ruby/Gems/2.3.0:/System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/lib/ruby/gems/2.3.0', execute `gem env` for more information
from /System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/lib/ruby/2.3.0/rubygems/specification.rb:1442:in `block in activate_dependencies'
from /System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/lib/ruby/2.3.0/rubygems/specification.rb:1431:in `each'
from /System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/lib/ruby/2.3.0/rubygems/specification.rb:1431:in `activate_dependencies'
from /System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/lib/ruby/2.3.0/rubygems/specification.rb:1413:in `activate'
from /System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/lib/ruby/2.3.0/rubygems.rb:196:in `rescue in try_activate'
from /System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/lib/ruby/2.3.0/rubygems.rb:193:in `try_activate'
from /System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:125:in `rescue in require'
from /System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:39:in `require'
from ./cdw-demo.rb:3:in `<main>'
Stack trace for Pry
/System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require': cannot load such file -- pry (LoadError)
from /System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from ./cdw-demo.rb:4:in `<main>'
The stack trace shows there maybe in issue with multi_xml being a missing gem, but that was installed with httparty
Gem list:
gem list
*** LOCAL GEMS ***
bigdecimal (default: 1.4.1)
bundler (2.1.4, default: 1.17.2)
cmath (default: 1.0.0)
coderay (1.1.2)
colorize (0.8.1)
csv (default: 3.0.9)
date (default: 2.0.0)
dbm (default: 1.0.0)
did_you_mean (1.3.0)
e2mmap (default: 0.1.0)
etc (default: 1.0.1)
fcntl (default: 1.0.0)
fiddle (default: 1.0.0)
fileutils (default: 1.1.0)
forwardable (default: 1.2.0)
gdbm (default: 2.0.0)
httparty (0.17.3)
io-console (default: 0.4.7)
ipaddr (default: 1.2.2)
irb (default: 1.0.0)
json (default: 2.1.0)
logger (default: 1.3.0)
matrix (default: 0.1.0)
method_source (0.9.2)
mime-types (3.3.1)
mime-types-data (3.2019.1009)
minitest (5.11.3)
multi_xml (0.6.0)
mutex_m (default: 0.1.0)
net-telnet (0.2.0)
openssl (default: 2.1.2)
ostruct (default: 0.1.0)
power_assert (1.1.3)
prime (default: 0.1.0)
pry (0.12.2)
psych (default: 3.1.0)
rake (12.3.2)
rdoc (default: 6.1.0)
rexml (default: 3.1.9)
rss (default: 0.2.7)
scanf (default: 1.0.0)
sdbm (default: 1.0.0)
shell (default: 0.7)
stringio (default: 0.0.2)
strscan (default: 1.0.0)
sync (default: 0.5.0)
test-unit (3.2.9)
thwait (default: 0.1.0)
tracer (default: 0.1.0)
webrick (default: 1.4.2)
xmlrpc (0.3.0)
zlib (default: 1.0.0)
Let me know if anymore information is needed.

Answer 1

Rather than using /usr/bin/ruby which is the system installed Ruby, use the hashbang
#!/usr/bin/env ruby
This should point to your global rbenv backed Ruby.