3 Easy steps to get cards without spending money:
1 Try to get as much free stuff from the game as possible
Daily rewards, reward ladder, trainer challenge, etc. , the game provides you with ample opportunities to earn free stuff.
2 Use your tickets to play Theme Deck tournaments
They are much easier to win than regular tournaments, especially if you don't have a competitive viable deck yet and yield the same rewards every other week (you can use the coin tournaments to practice and then play the ticket tournaments the week after).
3 Never open any trade-able item
Doesn't matter if it's a pack, or a chest. Those items are the main in-game currency (i.e. a Chest is currently valued 0.5 packs at TC, which means that you could trade 24 of them for a Zoroark GX, just to give an example).
Once you acquired a bunch of cards and packs, it's a good idea to look for a budget deck, that can still compete in the format of your desire. That way the game doesn't get stale and you have something to improve upon.
If you are willing to spend money on the game, the best solution is to buy code cards from 3rd party websites.
The shadows of the abyss are like the petals of a monstrous flower that shall blossom within the skull and expand the mind beyond what any man can bear, but whether it decays under the earth or above on green fields, or out to sea or in the very air, all shall come to revelation, and to revel, in the knowledge of the strangling fruit - and the hand of the sinner shall rejoice, for there is no sin in shadow or in light that the seeds of the dead cannot forgive...