Ask yourself a few questions:
1. Budget
2. Handload or factory ammo
3. Willingness to wait
The 30-06 can be a good long range caliber imho, I have one so I might be biased. The ADL (again imho) is not an ideal starting point as it is specifically a hunting configuration. The barrel is a light weight sporter designed for minute of deer. If you are willing to sink the $$ and wait time into building it, then you will need to scour the archives for Lake City Match ammo if you do not hand load. If you are looking to get shooting long distance sooner and cheaper, consider tabling the ADL 30-06 and looking for a .308 that is better designed for long range precision. If you do not hand load, the .308 will have a greater variety of match ammo available. Just my 0.02 YMMV.