1st Level Clerics typically serve their party best by acting as a tank.
Mechanically, when it comes to very low-level campaigns, the cleric has three jobs: Tanking, Preventing Death, and Secondary Damage Dealer
- Tanking: You can wear medium / heavy armor, wear a shield and use the dodge action. This combination is more potent than any specific buff or protection spell in your current arsenal, drastically reducing damage from 1-2 enemies per fight.
- Preventing Death: - Your healing spells (Spare the Dying, anything that cures 1 hit point) - prevents a player loss. Use your short and long rests to restore hit points out of combat, expending spells before resting. If someone is about to die - either press in and finish the fight or grab the still warm body and run. 1st level campaigns are lethal.
- Secondary Damage - Hit people with your weapon. The best medicine is damage down range. If the monster is dead - it can't deal damage. Inflict Wounds and Guiding Bolt can help out significantly for some much-needed spike damage at 1st and 2nd level.
Arguably everything else at 1st level (your spell list - feats - racial traits) is a matter of utility and flavor that is campaign specific. But as long as you make your armor a priority, keep spare the dying on tap, and memorize 1-2 copies of a damage spell you can keep your party alive long enough to get to the more interesting spells and tools in the clerics kit at higher level.
Let the bard do the buffing at lower level (if ones avalable). The best protection spell you can offer your party is yourself. And if your low on hit points... you are your own healer. If your fighter is about to go down, your standing right next to him. So get up front, channel your inner meat shield, and cast "Protect Party": Dodge Abuse".
There are only two feats at this level that arguably lose their value at higher levels (in comparison to taking something else or a solid ABI increase).
War Caster: Advantage on saving throws to maintain concentration while serving on the front line. It also can save your action economy when doing weapon storage / draws to cast spells with a shield on your arm.
Sentinel: Lets you use your reaction to potentially stop enemy movement, keeping your front line dressed and monsters from getting to your back line. It also allows for typically one reaction attack of opportunity per round if the enemy chooses to ignore you for trying to walk around you or attack the fighter your standing next to while taking the dodge action.
In both cases, at higher level the cleric spends less time adjacent to their front-line party members. Things like summons, walls, and control spells become more readily available to bottleneck monsters and protect the backline. If you are not taking this campaign to higher levels they can be worth a pick, but it is more valuable overall to take an ability score increase in wisdom or constitution.
Feat selections after this point is a matter of high-level combinations. The feats you would take at 1st level are very different if you plan on taking them to much higher levels. In either case, my recommendation is to take an ABI, or if your human, a feat you plan on using at higher levels.
Progressing out of 1st and 2nd level:
Pick up Spiritual Weapon upon reaching 3rd level. It synergizes with the Dodge action, allowing you to consistently attack while using bonus actions. Either allowing you to stay very defensive and contribute to damage downrange, or outright doubling your damage output.
About the time you reach 5th level, the difference in HP between you and your fighter / barbarian becomes noticeable - and you want to begin transitioning off the front line and into a mid-line role. Your tank is out front, and you can Lineback whatever gets past the fighter. It's at this point that buffs and other utility spells become more valuable than you standing on the front line.