https://github.com/protocool/AckMate - Searching within your project sucks by default. This makes it not suck.
Testing -
https://github.com/aslakhellesoy/cucumber-tmbundle - Bundle for cucumber highlighting. https://github.com/rspec/rspec-tmbundle - Lets you run specs individually from within textmate.
Frontend -
https://github.com/kuroir/SCSS.tmbundle & https://github.com/peterlih/handcrafted-haml-textmate-bundle & https://github.com/seaofclouds/sass-textmate-bundle - Sass/Haml/Scss bundles. HAML and Sass will make you life significantly easier, embrace them.
Next up, download and install : http://www.levien.com/type/myfonts/inconsolata.html
For themes, I prefer 'Blackboard' with the font changed to Inconsolata, but play around with the various color schemes and choose whichever you prefer. You'll probably spend a lot of time looking at it.
Now, bookmark: http://api.rubyonrails.org/ and pretty much keep it open somewhere all the time. It's invaluable for rooting through why things aren't working.
Lastly, rails is full of magic. Magic that sometimes is quite far removed from the actual errors you run into. Your first few months will probably have more than a few very frustrating moments where things just don't work and you can't figure out why. Stackoverflow is your friend, and no question is stupid. If you can't google an answer, just ask.