No way would I start over. I have spent a little on the game in about 1.5 years and its usually to get the $10 pack to get a marquee character to 4* just because I like playing with new things. Those dont get me an edge in arena at all. I'm in a guild that only recently started doing heroic tank and we do T4 Sith raid, get 27 stars in TB and have mediocre results in TW. I'm 30-60 range in arena and 1-30 range in ships. My Arena team is 10-15k less GP (Edit: I just looked and its actually 25k less) than everyone around me. I ran a 3* Sion and 4* Nihilus for a long time in top 100 -150 arena. You dont have to spend a lot of, or any, money. F2P Jedi are an option now too. And with TW and TB there is a use for some of the "weaker" characters that you may have.
Just have a plan and learn how to use mods. Most people still dont understand them or use them properly and they are the most important part of the game. A g10 or g11 Vader with good mods is way better than a g12+5 with crappy ones.