Depends on how much money you've got to spend. You can go from 52-99 in under 20 hours doing mith darts, but you'd lose 65-70m.
Your best bet is probably to just make willow bows (u) until you can make maple longbows (u), then make those until you can make yew longs, and make yew longs to 99 or until you can make magic longs. You probably wouldn't be able to get 99 in a week unless you where botting 24/7 tho.