Keep in mind the cost and dicepools involved. Unless there is a specific reason to keep THAT SPECIFIC SPIRIT around you are better off summoning a new spirit and binding it.
Summoning/binding dp of 18 and F6 spirits.
Summoning will average 4 net hits (or 8 with post edge)
Binding will average 2 net hits (or 6 with post edge) at a cost of 3,000¥
Your cost per bound service is between 500¥ and 240¥ (if you have the edge and boosted the limit) - this is your baseline.
If you are rebinding an already bound spirit you are spending between 1,500¥ and 500¥ (with edge). You are spending 2-3 times as much ¥ rebinding, and earning a bad reputation in the spirit community.
As long as the spirit you are summoning isn't greater than your MAG you can summon (and rest) a couple times - waiting till you get a good roll (find a compatible spirit) -> then post-edge. All you would be out is the reagents you used to boost the limit and perhaps a little rest time to recover from the drain.
Getting your DP up is critical. invest in a power focus - as expensive as they are they are worth it.