Im using Snapseed for most of my edits such as cropping, tuning image, changing the details etc. One thing good about snapseed is there are tutorials that teaches you on ways to create style for your photos, eg: applying a frozen effect, detailed black and white, fades and low key HDR. Additionally, you can also watch online YouTube tutorials on using snapseed as well (i've learnt how to recreate double exposure and cloning). So far im happy with snapseed and i recommend you to try it out.
Another alternative many used is VSCO where they have presets that you can apply to ur setting. However, some of these you will need to purchase. One preset that i loves using on VSCO is HB1 and HB2 (HB means hyberbeast). These two can be 'purchase' for free.
i believe both apps should be available on both android and apple devices.
Hope this helps!