If you are going for an experience. and speed, I would opt for Yaks, Experiments, Flesh Crawlers (SHoS), or maybe Rock Crabs. Each of RuneScape gold these categories will have an adequate flow of exp. and speed, in addition to being fairly casual and low risk.
For Summoning it is all about if you have the charms. If you have the charms the process will surely take you a mere day and possibly less. If not, nobody knows how long it will be to get them. I'll go with the assumption you have the charms.
From 22-31, make Granite Crab pouches. This is a fairly effective method in addition to costing tiny charms. You'll require about 1,300 empty pouches iron ore, and buy rs07 fire cape 10,000ish spirit shards. This is likely to cost you about mid to high 200k.