would sound counter productive and probably u have money to afford it anyway, but, the best advice one first time premium player need to receive is: DO NOTHING BUT SECURE YOUR SECOND PREMIUM TIME.
like... getting a second premium time in-game is easier than a first time, but ppl believes is as horrible as trying to get the first one.... nothing is farest from reality u can grind it playing healthy, like 4h a day doing 60k/hour during 30days. So if you can't afford a second premium time with money, the first thing that u need to do is start spending some time hunting for profit, there are several places for that and guides aswell where to get money as low lvl (below 100)
as said is really important that u use daily offline training and daiy reward. Now the second point is once you are sure u wouldn't waste 30d and never ever again be premmy, start getting familiarized with the stuff (isn't wise familiarizing first then being unable to use them) those are:
-hunting analyzer (worth for giving you tools to improve or know your hunting sessions stats)
-party analyzer and party window (worth only if you have friends, but help to teamhunt better and share better the profit/waste)
-charms (u can actually use charms being free... but aren't worth not even easily obtainable) here my advice is, hunting different kinds of mob till you unlock their whole entry on cyclopedia.
-preys (are for free too, but neither worth) u have now unlocked 2 entries of prey, use them wisely, my best advice is, learn first where u want to hunt if is really worth and what prey u would use, example: amazons for money u need to use loot prey. while mutated tiger for money specially if you are between 50-60, either loot, atk or damage reduction are worth.
(to save a type of prey u need to re-roll it before the time runs out, otherwise u would lose it or if u activate re-roll with cards that prey would change)
as said by others is wise aswell to do some grizzly addams task, sadly most of them are unworthy nowadays, but a few are really worth specially due the stats of mobs: tarantulas, apes, gargoyles (specially for mages)
mutated tiger, mammoths+badgers, tarantulas (specially for paladins)
third, learn about where to hunt and where NOT to hunt:
for me THIS is keypoint between a good new starter and a bad new starter, like, for some reason ppl that tibia is horrible and hard and pointless due during 30 days of premium they wasn't able to either farm their premmium back or get meaningful levels... Right Now in 30d u can hit lvl 150 more or less without pushing yourself too hard. specially if a mage, and that lie about mages does no profit is just that, a lie. So the third thing u need to do is find guides about what is wise on tibia to hunt in, once you secured your second premium time you can start either hunting to afford hunts for exp, or better Equipment, or so and you would climb without too many troubles, as again we don't klnow your vocation nor lvl is hard to advice you, but there are LOT of guides out there on internet so you can start there.
there are a lot of stuff to do on tibia as pointed already, and we don't know what lvl you are to give you specific aids, but those would help any low lvl to figure out what is more important.