Yes, kings did "give things away", but as in many premodern societies these "gifts" came with a catch ;). Irish kingship can be seen as an extension of the more general socio-economic hierarchy that underpinned Irish society. In this system, a wealthy individual (who in this context measured his wealth in the form of cattle, rather than money) would attract the attention of less prosperous individuals who wanted some of those cattle, as they could be used to increase their own personal wealth, pay legal fees, purchase goods and services and so on.

So the second individual would approach the first and enter a voluntary contract of clientship with the him. The type of clientship depended on one's status: those of low birth became doercheile (base clients) while poorer nobles became soercheile (free clients) which determined the amount of wealth they received and (this is where the catch comes in) the sorts of responsibilities that they would have to furnish for their lord. These included payments in food, participation in agricultural and manual labour for the lord and military duties.

This military participation in the patron's buiden (translated as "host", "band" or "troop") might actually have been beneficial for the clients themselves as their activities would have ensured the protection of their own property. Legal glosses explain that these military duties were divided into fubae; the destruction of pirates, violent criminals and wolves, and rubae; patrolling the frontier and strategic points of their local territory against hostile incursions.

So we've seen why a prospective client might seek to enter such a contract with a patron for purely economic reasons, but the system of clientship went much further than that. Clients and patrons benefited mutually from such arrangements in a number of crucial ways. Perhaps most importantly, both the client and patron earned substantial legal protection from their arrangement that would be unavailable to an individual living "outside the system". A client could look to his patron for support in legal matters, such as having him sign on as a prestigious surety for contracts made with other individuals (which I suppose is kind of similar to using a credit card through your bank). The patron, on the other hand, could use the support of his numerous clients in court cases to "outweigh" his opponents with testimony - one peculiarity of early Irish law was that legal outcomes could be decided by the side that furnished more oaths on their behalf than the other. Keep in mind that Ireland at this point was more or less a stateless society; people needed the support of others in the face of legal adversity and potential conflict.

Finally, a prospective patron would seek to cultivate a mass of clients despite actually losing or renting out his wealth in order to accrue status and prestige. Not only did they receive legal protection, a personal warband and freedom from manual labour by the services of their clients, but their own honour was quantitatively increased by their number of clients. In medieval Ireland, honour was a real, quantifiable thing that determined one's status in society and the kinds of contracts they could enter and the quality of their legal testimony. For an aspiring aristocrat, accruing status and prestige through taking on a multitude of clients would give authority to the political, legal and military power that those clients themselves furnished him.

So the system of clientship was much more complicated than a simple exchange of gifts. Both clients and patrons thought the arrangement was advantageous for a multitude of reasons; the exchange of wealth ensured economic prosperity, legal protection, military power and status.