That's good advice from knightdk. I would add that you should consider convenience and risk in your calculation. Full nodes offer the best security and one can use them with systems like paper wallets to secure millions of dollars. They do, however, require some understanding and frequent syncing. If you only want to try out $100 worth of bitcoin then you might choose a phone wallet like (
https://play.google.com/store/apps/details?id=de.schildbach.wallet ). A little less secure, but easy to use when paying. I keep some in this wallet, less than the cost of the phone. Then I keep the main wallet offline in a bank vault.
The absolute most important thing you can do is BACK UP YOUR WALLET!!!!!!
As long as you have a backup even If you lose your phone everything is fine. If you don't have a backup then your bitcoin is hopelessly lost. So make a copy, put it on a USB or a paper wallet, put it in a bank safe deposit box
before funding the wallet.