As the name suggests, Premodern uses cards from before Modern, with sets ranging from 1995 - 2003, dodging the broken cards of Magic's early years and the higher powered creatures that have emerged more recently
The most important part of its effect is its ability to tribute a Dinowrestler monster, including itself, to destroy a card on the opponent's side of the field
Into the Inklands sapphire cards continue this trend by introducing a collection of new cards that take more advantage of the item cards in the game, as well as providing excellent opportunities for card draw, gaining more ink and cards that just have great stats
However, assuming that you're building a fairly typical deck, there is a really simple way of figuring out about how many lands you should put in your deck
$15/box or $40 for all 3 boxes
To determine the total cost of a spell, start with the mana cost or alternative cost you're paying, add any cost increases, then apply any cost reductions (such as that of Saheeli's second ability)