I'm a career blm of 60. Blm is tough in the beginning. I recommend duoing with a melee once the solo experience begins to plummet around level 6 or so. Two of the reasons the 5-10 level stretch is so rough as a blm is because the mobs that give bigger exp now outlast your mp, and your hp is still too small to melee safely. I remember many times I would engage a Giant Bee (the second tier bee in saruta) and simply lack the endurance to win. Picking the right battles is crucial as a blm. The second reason the 5-10 stretch is rough is because it's long and boring. Having a friend out there with you can make even the most tedius job fun, it'll also provide you with the endurance to handle tougher mobs with less down time. A full party at this level won't be very efficient, but duoing always works wonders when I level new jobs.

As for what to do in a party, and curing- remember that you were invited for your main job first. I agree that every mage should be able to offer backup healing to the party. That said, you aren't the main healer, and your cures are best saved for emergencies. Your job is to make the enemy's HP drop in chunks, instead of slivers. There will be parties where you're the only one dealing noticable damage to a mob. Your job is to let the party get to chain 5, where they wouldn't have if the rest of the party had taken 10 minutes per mob. Along with Rangers, your damage capacity is top notch, and other jobs will have a hard time matching it. That's why you were invited to the party. Make the mob dead. After battle, if you have lots of excess mp compared to the main healer, use your excess to toss a curaga and top off the pt HP. If things go sour and you can save the party with a well placed cure, then by all means, do so, but don't let people give you the Summoner treatment.