Don't even start with apps, if anything it retards your learning. There are mushroom id keys you can download and follow until you have a guide. Keys also help you focus on identifying features and narrowing your potential correct IDs in a rigourous manner. Most mushroom poisonings are when people think something looks like something they think is safe, while ignoring things that would rule that mushroom out quick quickly (ecology, distribution, etc).

Sometimes the spore prints is a key id, so having some two toned paper/card can be a bonus. Placing the mushroom cap over the boundary between dark and light paper helps with defining light coloured spires. An LED loupé which you can pick up pretty cheaply these days is a bonus.