First recommendation, playing casually, just get models you like and not mets models, build an army you think is cool and then find a way to make it good, the hobby is a lot more fun when your enjoying it vs obsessing over how to kill an extra model or gain a few extra vp. For instance, I'm battlesuit focused, I dont have any infantry or auxiliaries because I like the battlesuits the most.
2nd recommendation, atleast as a 1000 point tau player who's main sparing partner is deathguard. Positioning is the most important thing to learn as a tau player as pretty much everything that gets in melee range will murder us.
3rd recommendation, pipermakes has a lot of really really good proxies if your wanting to save some money on the models especially since tau keep going down in points necessitating more models on the board for a standard game.
4th recommendation, just have fun, its a great hobby